Laws of cooking on Shabbos
The following chapter will discuss the laws of cooking on Shabbos.
The first section will discuss the ramifications of one who has transgressed and cooked, or did any other forbidden activity on Shabbos. At times the Sages decreed that the food be forbidden forever, at other times the food is forbidden until after Shabbos, and at others the food is even permitted on Shabbos as will be explained below.
The second section deals with the laws of cooking, it explains the definition of cooking and the prohibitions involved in heating foods on Shabbos.
Part 1: The law of food of which one transgressed a prohibition with on Shabbos
The intentional transgressor: One who cooks on Shabbos, or did one of the other [Biblically prohibited] actions, with prior knowledge of the prohibition is forbidden for him to ever benefit from that action that was done due to a fine.
The law of the pot: As well, the pot in which he cooked in is forbidden [to be used by him] forever [until he kashers it], being that it is absorbed with an item that is forbidden for him.
The other people: However for others it is allowed [for them to benefit from] even the food immediately after Shabbos without needing to wait the amount of time it took to cook it [on Shabbos], even if it was [originally] cooked [by the transgressor] on their behalf.
The reason for not needing to wait until enough time passed after Shabbos to have been able to cook it is: because [the Sages] only required one to wait this amount [of time] by a gentile which does [a forbidden action] for a Jew, as in such a case if [the Jew] were to be allowed to benefit [from the food] immediately after Shabbos there is room to worry he may tell [the gentile] to do so on Shabbos in order so [the food] be ready for him immediately after Shabbos.
[The reason that we suspect for this is] because the prohibition against telling a gentile [to do a forbidden action on ones behalf] is considered light in the eyes of people.
Similarly [this decree as well applies] even when a Jew does [a forbidden action] in a case that he started from before Shabbos to do something that was forbidden to be started as was explained in chapter 253 [Halacha 1], as this prohibition too is light in the eyes of people and there is thus worry that one will transgress it in order so [the food] be ready [for him to eat] immediately after Shabbos.
Therefore [in the above two cases the Sages] required even others to delay [benefiting from the food] until enough time has passed after Shabbos to have been able to cook it.
[The decree even includes other people] due to a decree that [otherwise] one may tell another person to start [cooking it for himself and others] from before Shabbos. However [by other prohibitions done on Shabbos the Sages] were not worried at all that one may tell a Jew to do for him the prohibited action on Shabbos in order for him to be able to benefit from it immediately after Shabbos. Furthermore, [besides for the fact that we do not suspect a Jew of stooping so low to have another Jew transgress for him, even if a Jew were to ask another Jew to do so for him] the Jew would not listen to him being that people do not sin [on behalf of someone else] without self benefit.
The Unintentional transgressor: Similarly if [the forbidden action] was done by mistake, then it is forbidden [to be benefited from] on Shabbos even by others, as since he did a Biblical prohibition [the Sages] were stringent to fine [from benefiting from it] on Shabbos just as if it was on purpose in which case it is forbidden also for others.
The reason for this decree by an even unintentional transgression is: due to a decree that [otherwise] one may intentionally cook it and then say that it was done unintentionally.
After Shabbos: However in the evening [after Shabbos] it is immediately permitted [to be benefited from] even by the transgressor himself and he does not need to wait until enough time has passed after Shabbos to have been able to cook it for the reasons explained [above].
What is defined as an unintentional transgression?
If one committed [a transgression] due to the instructions of a Scholar which [he now knows] has made a mistake, then this is considered unintentional.
The same applies for one who forgot that it was Shabbos or [forgot] that [the act that was done] is forbidden.
Is the food allowed to be eaten after Shabbos if that night is Yom Tov?
If Yom Tov falls out on the evening after Shabbos then [food which was cooked on Shabbos] is forbidden until after Yom Tov, because [on] Shabbos [one] is not allowed to prepare for Yom Tov.
Other Opinions: [However] there are opinions which say that there is no preparation involved in this case for the reasons that will be explained in chapter 501 [Halacha 18].
The Final Ruling: One should suspect for the first opinion [and thus not eat it until after Yom Tov].
What is the law if the forbidden food fell into other foods after Shabbos?
Mixed in after Shabbos: If one intentionally cooked [food on Shabbos] and after Shabbos that food got mixed into other foods, then it is nullified in majority [of the Kosher food].
The reason that the food is not considered something which has a permitted side to it: It is not considered something which has a permissive side, meaning [that we do not say that since] other people can eat this mixture without any prohibition at all even without [the food that was cooked on Shabbos] being nullified in majority [therefore it is considered a food that has a permitted side], because something is only categorized as having a permitted side if [the food] will become permitted for the person that it was forbidden for. However here without it being nullified in majority it is only permitted for other people to which the food was never prohibited for them at all from after Shabbos and onwards.
On Shabbos: However if it mixed on Shabbos, then since on that day it is considered something which will eventually become permitted for others due to which it is now not nullified in majority, [therefore] it is considered something which will become permitted also for the person who cooked it and this mixture [thus] becomes forbidden to him forever.
Is food that had a transgression done to it on behalf of an ill person allowed to be eaten by others?
Eating from meat of an animal permissibly slaughtered on Shabbos: One who slaughters on Shabbos on behalf of a deathly ill person, it is permitted for a healthy person to eat from this meat while raw, without salting it [for blood] but rather with merely rinsing it alone as is explained in Yora Deia chapter 67 [Halacha 2], because it is forbidden to salt on Shabbos as will be explained in chapter 321 [Halacha 2].
[Furthermore] even if the sick person received his illness today [on Shabbos] and [thus] yesterday [before Shabbos] he did not have in mind at all to slaughter [the animal] today [on Shabbos], nevertheless it does not contain [the] Muktzah [prohibition], for the reason explained in chapter 310 [Halacha 6].
Eating from food cooked or that had done to it any other forbidden action on behalf of an ill person: However one who cooks, or does another type of [forbidden] action for a deathly ill person, then it is forbidden [for that cooked food to be eaten] on Shabbos by a healthy person or by [even] a sick person who is not deathly ill.
The reason for why one may not eat from the cooked food is: due to a decree that [if he were allowed to eat from it then] he may come to add [meat] for himself to the [forbidden] action [being done].
However by slaughtering, adding [more to the action being done] on behalf of a healthy person is not relevant, as it is not possible to [obtain] a Kezayis of meat that one needs for the sick person without slaughtering the entire animal.
The law when a gentile did a forbidden action to the food on behalf of an ill person: [Furthermore] even if one did [the forbidden action of cooking and the like] through a gentile, whether it was done on behalf of a deathly ill person [or] whether on behalf of a sick person who is not deathly ill, it is forbidden for a healthy person [to partake in that food] on Shabbos, due to a decree that [if this he were allowed to partake in it] perhaps he may [tell the gentile] to add [more food] on his behalf.
However after Shabbos it is allowed [to be eaten] by a healthy person immediately, and he does not have to wait the amount of time after Shabbos that it would have taken to cook it being that the gentile which did [the forbidden action to the food] was permitted [to be told to do so being that it was] for the need of a sick person.
If the gentile cooked or baked the food: However this [allowance to eat the food after Shabbos] only refers to [when] other [forbidden] actions [were done to the food on Shabbos by the gentile] with exception to baking and cooking, as if a gentile baked or cooked on Shabbos for the need of a sick person, then it is forbidden for a healthy person even after Shabbos due to it containing [the prohibition of eating] food cooked by a gentile, as will be explained in Yora Deia chapter 113 [Halacha 1].
Fruits that were cut down on Shabbos on behalf of a sick person:
The fruit was not yet ripe: One who cuts down an unripe fruit on behalf of a sick person on Shabbos then [that fruit] is forbidden [to be eaten or even moved] by a healthy person [on Shabbos] being that it is Muktzah. [This applies] even if the person was [already] sick from before Shabbos, and one already had in mind from before Shabbos to cut down the fruit on Shabbos.
The reason for this is: because designating [a Muktzah item from before Shabbos] does not help at all by [items that are] connected [to the ground] in cases that it is still growing and ripening on Shabbos.
The fruit is completely ripe: However if the fruit has finished ripening and no longer will continue to grow, designating it [before Shabbos] does help [to remove its Muktzah state and allow it to be moved in the above scenario] even though it was attached to the ground [on Shabbos].
Part 2: The cooking prohibition
The following laws mainly deal with what constitutes the Biblical prohibition of cooking on Shabbos and not the Rabbinical prohibition associated with placing cooked food on a fire on Shabbos. Regarding when one may place a food on the fire even when the food does not contain a cooking prohibition, see chapter 253 where these laws are discussed extensively.
The Principal prohibition: Cooking [on Shabbos] is one of the Principal [forbidden] actions, being that in the Tabernacle [colored] herbs would be cooked in order to dye with.
Frying, baking and roasting: Not only is cooking in water alone included [in this prohibition], but even frying, and baking and roasting, are included in [the] cooking [prohibition].
Melting and hardening: As well anyone which has melted a hard item with fire, such as one who softens one of the types of metals, or heats up the metal until it becomes [as red as] a coal, or melts wax or fat or tar and sulfur with fire, or hardens a soft material with fire, such as one who places clay vessels in fire until it becomes an earthenware vessel, he is liable for cooking.
Cooking on fire heated objects: Similarly, just as it is forbidden to cook with fire so too it is forbidden to cook with an item that received its heat from fire. For example [it is forbidden] to place an egg near a pot that was heated from fire or to break [an egg] on a cloth that was heated from fire, in order [for the egg] to fry a little bit, and [thus] if it was fried there to the point of the food of Ben Drusaiy then he is liable for cooking just like if he had fried it [directly] on a fire.
Cooking on sun heated objects: Furthermore even [cooking] with [an item that was] heated from the sun, such as [cooking] on a cloth that got hot in the sun, is forbidden due to a decree [that is this were to be allowed then] one may come [to also cook on an item that] was heated through fire, as one who witnesses [a person cooking on such a cloth] thinks that the cloth was heated with fire.
Similarly it is forbidden to roll [the egg] on sand, and road dust which have become hot from the [rays of] the sun, and it is forbidden to insulate [food] in them even from before Shabbos due to a decree [which was decreed because if this were to be allowed then] one may come to insulate with embers as explained in chapter 257 [Halacha 1].
Cooking with direct sun heat: However [to cook] with the [heat of the] sun directly, such as to leave an egg in the sun in order to cook, or to leave water in the sun in order to heat up is allowed because doing so is not the common form of cooking [and thus is not Biblically forbidden]. [Furthermore it is even Rabbinically permitted as the Sages] did not decree [against cooking] with the sun due to [that one may then also come to cook] with fire being that [cooking in the heat of] the sun will not be confused with cooking with fire.
Cooking in hot springs on and before Shabbos:
One who cooks in the hot springs of Tiveria is exempt [from liability], because they are comparable to an item heated by the sun. Nevertheless it is Rabbinically forbidden [to cook in it] even if the food is positioned on top of [the spring] and thus cooks from above.
However it is allowed to position it there from before Shabbos, although to insulate it completely inside [the spring] is forbidden even from before Shabbos due to the insulating prohibition, as will be explained in chapter 326 [Halacha 3].
Heating an item that was previously cooked:
A precooked liquid that cooled below 110 Fahrenheit: All liquid substances are [forbidden to be] cooked [even] after having been previously cooked. Thus a liquid dish which was already fully cooked and cooled off, even if it did not cool off completely but is no longer [hot to the point of] Yad Soledes, then if one heats it on Shabbos until it reaches [the heat of] Yad Soledes, he is liable for cooking. 
A liquid which is still 110 Fahrenheit or above: However if it [the precooked liquid dish] was [still] hot to the point of Yad Soledes and one then heated it even more, there is no cooking [prohibition involved]. [Furthermore this food] is allowed even initially to be [further] heated near a fire in a scenario that [the Sages did] not [prohibit this due to] a worry that one may come to stoke [the coals] as will be explained [in Halacha 24] (and whether it is [also] allowed to be placed on a Kirah or Tanur oven was explained in chapter 253 [Halacha 14-29]) [See Q&A on summary of heating precooked liquids.]
Other Opinions: [However] there are opinions which say that even if [the precooked food] has [already] completely cooled down there is no [prohibition in] cooking it after [it having been previously] cooked, and it is thus allowed to be heated on Shabbos near a fire in a situation that no suspicion exists that one may come to stoke [the coals].
The Final Ruling: The custom is to be lenient if [the liquid food] has not yet completely cooled down and is rather still fit to be eaten due to its heat. However if it completely cooled down we are accustomed like the first opinion [to prohibit heating it], even regarding a case that one already heated it [and thus the food would be forbidden to be eaten] as was explained in chapter 253 [Halacha 25]. Even to place it on top of a heater prior to it being lit by a gentile in order for it to heat up when it gets lit is forbidden as explained there [in chapter 253 Halacha 27]. Similarly [the custom is to be stringent] regarding doing anything [to this liquid] which involves a cooking prohibition.
Cooking foods that are not yet fully cooked:
All the above [discussion] refers to food that has already been fully cooked, however any [food] which has not yet been fully cooked, even if it was already cooked to the point of the food of Ben Drusaiy, [nevertheless] it retains the cooking prohibition even if it is currently boiling.
Hastening its cooking through stirring: [Furthermore it is forbidden] even if it will cook on its own and one simply does something to hasten its cooking such as stirring it with a spoon.
Placing food in a Keli Rishon and Keli Sheiyni
Fully cooked dry food: Dry food which contains no liquid at all is [permitted to be] cooked after having been previously cooked as long as it was already fully cooked, even if it completely cooled down.
It is even allowed to soak it in a hot Keli Rishon [I.e. any pot that was previously on a fire] in order so it dissolves there and become a liquid substance. [However according to the Siddur, which is the final ruling, it is forbidden to heat it in a way that it will dissolve and reach a heat of Yad Soledes.]
Uncooked dry food: If [the food] is dry and has not been [fully] cooked before Shabbos, one may not soak it on Shabbos in hot [liquidly] food that is Yad Soledes even if it will not dissolve in there at all. If one [transgressed and] soaked it in a Keli Rishon then he is liable, and soaking it in a Keli Sheiyni is Rabbinically forbidden being that it appears like cooking.
The reason why spices are allowed to be placed into a Keli Sheiyni: [Placing a raw dish into a Keli Sheiyni] is not similar to spices, which is allowed [to be placed] in a Keli Sheiyni as will be explained [Halacha 12], being that spices are made to flavor the dish and it [thus] does not appear like cooking.
Onions and Garlic: Similarly any food that is made to give taste to a dish, such as garlic or onions, are considered like spices and are allowed to be placed into a Keli Sheiyni even if it is [the heat of] Yad Soledes.
Other Opinions by onions: [However] there is an opinion which questions regarding onions that perhaps it too cooks in a Keli Sheiyni so long as it is [the heat of] Yad Soledes.
The Final Ruling: The custom is to be lenient.
Other Opinions regarding a Keli Sheiyni: There are opinions which allow any dry item that has not yet cooked to soak in a Keli Sheiyni [even if it] is Yad Soledes.
The Final Ruling regarding placing uncooked dry foods in a Keli Sheiyni : One is to be stringent in this like the first opinion.
Iruiy Keli Sheiyni [pouring from a Keli Sheiyni onto uncooked foods]: However it is permitted to pour from a Keli Sheyni that is Yad Soledes onto anything which is dry [even if it] has not been [previously] cooked.
Pouring on foods which are very lightly cooked: [This allowance to pour from a Keli Sheiyni is] with exception [to pouring onto] the type of fish called “Little Tunny” (Euthynnus Alletteratus), and an aged salted food such as salted meat or fish from the previous year, [being] that they only require a slight amount of cooking and this pouring [from a hot Keli Sheyni] finishes the act of its cooking, and one is [thus] liable on it for [the] cooking [prohibition]. Nevertheless it is allowed to soak it and wash it in cold water.
The same applies for any [food] that is hard which one did not [previously] cook and can become edible through soaking it or washing it in hot water, then if one soaked it even in a Keli Sheiyni, or rinsed it even with the pouring of a Keli Sheiyni and it [then] became edible, one is liable for cooking.
Similarly any [food] which was not [yet] cooked, that it is very salty and is not edible until one soaks it or rinses it in hot water, then if one soaks it or rinses it in hot water he is liable.
However it is permitted to soak and wash it in cold water even if it becomes edible through doing so, being that it is permitted to turn inedible items into food on Shabbos as will be explained in chapter 324 [Halacha 4].
Cooking a roasted or baked food on Shabbos
There are opinions which say that although there is no [prohibition in] cooking an already cooked [food] that is dry, nevertheless there is [a prohibition to] cook [food] that has been previously baked or roasted, and [thus according to them] if one places baked or roasted [food] even while still burning hot into a Keli Rishon that is Yad Soledes, he is liable. Accordingly even regarding [placing these foods] into a Keli Sheiyni one needs to be stringent Rabbinically as was explained above [in the previous Halacha].
One therefore needs to be careful not to place baked bread even into a plate [of food] that is a Keli Sheiyni so long as it is Yad Soledes.
Other Opinions by Keli Sheiyni: There is an opinion which questions and suspects [that there is] a sin offering liability [involved] also [in cooking] in a Keli Sheiyni that is Yad Soledes, being that there are delicate foods that cook even in a Keli Sheiyni and we are not experts [as to which foods are delicate and which are not], and [thus] perhaps bread is also considered delicate in this regard and it thus cooks in a Keli Sheiyni which is Yad Soledes [and is thus liable]. This doubt as well applies by other foods.
The Final Ruling regarding what may be placed in a Keli Sheiyni: One should be stringent regarding all [uncooked foods and thus avoid placing them in a Keli Sheiyni] with exception to spices which the Sages explicitly permitted to be placed in a Keli Sheiyni, as well as water and oil as will be explained [Halacha 22], and the same law applies for other liquids.
Even by roasted meat one is to be stringent [not to place it in a Keli Sheiyni] being that [one is liable for] cooking [a food] that was previously roasted.
However by cooked [meat] there is no need to be stringent at all, even regarding [placing it] into a Keli Rishon, as according to all opinions there is no [prohibition in] cooking [an] already cooked [food] that is dry.
Other Opinions by a roasted and baked food: However there are opinions which permit by a baked and roasted food, even if cold, to place them even into a burning hot Keli Rishon, being that [according to them] there is no [prohibition to] cook [a food that has been] already baked or roasted.
The Final Ruling: It is the custom to initially be careful like the first opinion to not place bread even into a Keli Sheiyni so long as it is Yad Soledes, although if one did so it is permitted [to be eaten on Shabbos] even [if one placed it] in a Keli Rishon, as rules the latter opinion.
Baking and roasting an already cooked food:
According to the first opinion that there is [a prohibition in] cooking an already baked and roasted [food] there is also [a prohibition to] bake and roast [a food that has] already been cooked. Meaning [that according to them] any [food] that is cooked is forbidden to be placed without [warm and precooked] liquid near a fire by an area that it is able to heat up to the point of Yad Soledes.
Baking and roasting an already baked or roasted food: However according to all opinions there is no [prohibition to] bake and roast an already baked and roasted [food] and [thus] a food which is baked or roasted is allowed to be placed near a fire in the way that will be explained [in Halacha 24], even if it has already completely cooled down.
Placing even uncooked food on top of an Insulated pot:
A vessel which contains a hot food which is Yad Soledes is permitted to be placed on top of a pot which is insulated in clothes in order so it retain its heat and not get cold.
If the food is not yet fully cooked: [Furthermore] even if [the food in the upper pot] is not yet completely cooked in which case doing something to hasten its [further] cooking contains the cooking prohibition, nevertheless [here it is allowed to place it on top of another insulated pot which is not on a source of heat] being that it is impossible for it to become completely cooked through doing so and that it cannot even further cook it, and it rather only retains its heat.
Sealing the cover of a pot on Shabbos: [As well] it is allowed to seal the lid [of the upper pot] with dough in order to retain its heat if he has dough that was kneaded yesterday [and was designated for this purpose and is thus not Muktzah].
However it is forbidden to insulate it under clothes as explained in chapter 253 [Halacha 14].
If the lower pot will heat the food to the point of Yad Soledes: However one may not place a vessel which has in it [food that] is not hot to the point of Yad Soledes on top of [another] pot which is so hot that it can heat the upper [pot] to the point that it will become Yad Soledes.
The same law applies to placing [a pot] on top of a kettle which is this hot.
However this only applies when the [food in the] upper [pot] has not yet fully cooked in which case it contains the cooking [prohibition] even when hot.
If the food is fully cooked: However if it was already fully cooked but cooled down a little, then even though it is not hot to the point of Yad Soledes, [nevertheless] since it is [still] slightly hot to the point that it is edible due to its heat, then it was already explained that the custom is to be lenient that [re-heating] it does not involve the cooking prohibition and it is [thus] permitted to be placed on top of a pot or kettle [even] in order to heat it a lot.
[Furthermore] if [the food] is something dry that has completely cooked, then even if it has cooled off completely, there is no cooking [prohibition] involved in [heating] it, and it is [thus] permitted to heat it on top of the [pot and kettle], even if it will become Yad Soledes.
Placing cooked food on top of a pot that is on a fire:
Even if the pot was insulated on top of a fire [from before Shabbos], such as on top of a Kirah oven which has not been swept or covered, in the ways explained in chapter 253 [Halacha 8] [that it is permitted to be done in], and similarly if a kettle is on a fire, one is allowed to place on them on Shabbos any food which does not contain the cooking [prohibition], such as [fully cooked] dry food even if it is [now] completely cold or [fully cooked] liquidly food which has not completely cooled down, for the reason explained in chapter 253 [Halacha 26].
The laws of entering non-cooked foods into a Keli Rishon
Spices: A Keli Rishon has the ability to cook so long as it remains the heat of Yad Soledes even after one has removed it from the fire. Therefore it is forbidden to place spices in it.
If the Keli Rishon is no longer Yad Soledes: [Furthermore] it is proper to abstain from placing spices in a Keli Rishon even if it is no longer Yad Soledes, in order to distance [oneself] and make a fence around the matter [so that one not come to transgress the prohibition of placing spices when it is Yad Soledes].
Salt that has not been abstracted through cooking or evaporation: However salt is allowed to be placed inside [a Keli Rishon that is Yad Soledes] being that one had removed it from the fire, as salt requires a long amount of cooking similar to ox meat and does not cook unless it is on a fire.
Ox Meat: Nevertheless, ox meat is forbidden to place inside a Keli Rishon [that is off the fire] as although the meat [itself] will not cook, nevertheless the moisture that is on it will cook. Although if [the meat] is completely dry and does not have on it any moisture at all [then it is allowed]
Other opinions: [However] there are opinions which say that salt only requires a slight amount of cooking and is thus forbidden to be placed even in a Keli Sheiyni so long as it is Yad Soledes.
The Final Ruling: One who is strict will be blessed.
If one transgressed and placed spices into a Keli Rishon: If one transgressed and placed salt even in Keli Rishon, even if it is on the fire, in which case he transgressed a prohibition, nevertheless the food is permitted [to be eaten on Shabbos] as the salt is nullified against the food. [However] there are opinions which argue and prohibit the food until after Shabbos.
Salt that has been abstracted through cooking:
[However] all the above refers to salt which has not been [extracted through] cooking, however salt which has been extracted through cooking water is permitted to be placed in a Keli Rishon according to all opinions being that there is no [prohibition to] cook an already cooked [food] that is dry even if it dissolves through this second cooking as was explained above [in Halacha 11].
Nevertheless one who is stringent in this just like by other salt [which is not cooked], will be blessed.
Iruiy Keli Rishon/Pouring from a Keli Rishon onto uncooked food
Pouring onto spices: It is forbidden to place spices in a plate and pour onto them from [the content of] a Keli Rishon which is Yad Soledes, being that the pouring from a Keli Rishon cooks the outer layer [of the food that it is poured on].
If one transgressed and poured it: If one [transgressed and] poured it, then the outer layer is forbidden being that it was cooked on Shabbos.
A Keli Sheyni: However if one first poured from the Keli Rishon onto [an empty] plate, it is permitted to afterwards place the spices onto the plate.
The reason for why a Keli Sheyni is allowed as opposed to a Keli Rishon is: because the heat of a Keli Sheiyni does not have the strength to cook. [Furthermore] even according to those opinions which are stringent regarding a Keli Sheiyni within the Dietary laws of Kashrus, being that they hold that [the heat of a food in a Keli Sheiyni] has the ability to absorb and to give off [taste to another food which comes into contact with it] so long as it is Yad Soledes, nevertheless [here they also agree that one may place spices in a Keli Sheiyni] being that it does not have the strength to [actually] cook even when it is Yad Soledes.
It is not similar to a Keli Rishon which has the ability to cook so long as it is Yad Soledes, being that a Keli Rishon [receives this ability] due to its standing (near the fire) on the fire [which causes] its walls to become hot and [have the ability to] retain heat for a long time. Therefore [the Sages] considered [that it has the ability to cook] so long as it is Yad Soledes. This is opposed to a Keli Sheiyni which its walls are not hot and [the food] thus continuously cools off. [Thus the Sages do not consider it to have the ability to cook].
A bathtub filled with very hot water is not considered a Keli Sheyni
A bathtub that is filled with hot water, even though it’s [water is considered] a Keli Sheiyni, [nevertheless] it is forbidden to pour cold water into it.
The reason for this is: because since the hot water in it is meant for washing it can be assumed that it is very hot and [thus] will cook the cold [water] which gets mixed into it.
Pouring hot water into cold water:
However one is allowed to transfer hot water from this bathtub into another cold bathtub. [Furthermore] even [water of] a Keli Rishon, is permitted to be poured onto cold water.
The reason for why one may pour from a Keli Rishon into cold water is: because [the Sages] only said that the pouring of [the content of] a Keli Rishon cooks when pouring hot [liquid] onto spices and the like being that the hot [liquid] does not literally get absorbed into the food and rather hits it [from the outside] with its stream and thus cooks it. However [when] water [is poured into] water it actually mixes and [thus] the stream does not have the ability to cook the water that is underneath it, and rather the water that is underneath it overpowers it and cool off the upper water [that was poured onto it].
A Davar Gush/Placing a solid substance onto a food or liquid
However it is forbidden to place a piece of hot meat which is Yad Soledes into cold [liquid] gravy.
The reason for this is: because since [the meat] does not actually mix into the gravy, it thus cooks the outer layer that surrounds [the gravy] prior to the gravy having a chance to overpower it and cool it down.
Placing cold water into an empty Keli Rishon
A small amount of water: A kettle from which one has removed its hot water is forbidden to have placed into it a small amount of cold water being that [the kettle] is able to heat it up to Yad Soledes.
A large amount of water: However it is allowed to place in it a large amount of cold water in order to warm it up.
The reason that doing so does not involve the “fixing a vessel” prohibition: Now, although through placing cold water into it one forges and strengthens [the kettle] and it is thus found that he has fixed a vessel, as this is the method used by copper and steel smiths. As they place hot steel and copper into cold water in order so it hardens and strengthens, and this is [considered] the finishing act done by the blacksmith, as fire stretches the metal and brings it close to shattering while water strengthens it. Nevertheless since [here] one does not intend to fix the vessel, and rather only [intends] to warm up the water, it is allowed [to place water into it], as [in this case the forging of the kettle] is not inevitable [when one places cold water in it]. As before one forges a vessel it is heated to very high [temperature], while here it is possible that the [kettle] will not reach [this high temperature which it requires for] its forging due to the [cold] water [that was placed into it] preventing it from heating up so much.
Pouring water into a Keli Rishon and Keli Sheiyni
A small amount of water: It is allowed to pour cold water, even a small amount, into hot water that is Yad Soledes that is in a Keli Sheiyni, although not into hot water that is in a Keli Rishon.
A large amount of water: [However] if there is so much cold water [being entered into the Keli Rishon] that it is impossible [for the Keli Rishon] to heat it up until it reaches Yad Soledes, and rather it will only thaw its coldness, then it is allowed [to pour it] even into a Keli Rishon as long as it is not on the fire.
Placing a bottle of water into hot water
Into a Keli Sheiyni: It is permitted to place a bottle of water or of other cold liquids into a Keli Sheiyni which has hot water.
([Furthermore, it is even allowed] to insulate it completely inside [the hot water], being that it is permitted to insulate a cold item in a material that does not add heat, as explained in chapter 257 [Halacha 9] and hot water [that is off a fire] is considered an item that does not add heat as explained in chapter 258 [in the Kuntrus Achron there])
Into a Keli Rishon: However it is forbidden to place it into a Keli Rishon even only in order to thaw out the coldness, due to a decree that one may forget and leave [the bottle] there until it [reaches] Yad Soledes [which is considered to have cooked the water].
Into a hot bathtub: [Furthermore] it is forbidden to place [the bottle] even into a bathtub that had drawn into it the hot springs of Tiveria directly from the spring, [such as one channeled the spring water into the tub], because it [a tub] is Rabbinically considered like a Keli Rishon.
Rather one should enter water from the tub into a second vessel and then place [the bottle] into it.
Placing uncooked and cooked foods near a fire on Shabbos:
Cold Water: It is permitted to place a bottle of water or of other liquids opposite a bonfire in order to thaw out its coldness, as long as that one places it a distance from the fire to the extent that it will not be able to heat up in that place to Yad Soledes even if it were to remain there for a long time.
However it is forbidden to place it near the fire in a place where it can heat up to the point of Yad Soledes.
[Furthermore] to even leave it there for a short amount of time so it merely thaw the coldness alone is forbidden due to a decree that one may come to forget and leave it there to the point that it will reach Yad Soledes.
Placing raw fruits and the like near a fire: This same law applies for fruits or other foods which are eaten raw, that even though they do not need to be cooked nevertheless if one cooks it he is liable. Therefore it is forbidden to place these [fruits] by an area where they can get cooked if left there for a long time, which is defined as any place where it can reach Yad Soledes.
Cooked foods and liquids: However any [food or liquid] which does not have a cooking prohibition [applicable to it], is permitted to even be boiled near a bonfire.
For example a liquidly food which was completely cooked and is still hot to the point of Yad Soledes, or even if it is not [hot anymore to the point of] Yad Soledes, but it has not completely cooled down [which] according to the custom explained above [in Halacha 9] [which is] that it has become accustomed to be lenient [by precooked liquids even if it has cooled below Yad Soledes but is still warm], or [another example] even if [the food] has completely cooled down but it is a food which was baked or roasted [and is thus dry] [in which case we hold] that there is no [prohibition] to bake or roast an already baked or roasted food even if it has completely cooled down, as explained above [in Halacha 13] [then in the above cases it is allowed to even boil these foods near the fire].
The prohibition to place it on or very near the fire: Nevertheless, [the Sages] only permitted [placing even precooked foods] opposite the bonfire however to place it on the fire itself, or even very close to it is forbidden. Rather one must distance it a little bit [from the fire].
The reason for this is: because there is suspicion that he may come to forget that its Shabbos and will come to stoke the coals. However through requiring him to slightly distance it [from the fire] this then serves for him as a notice and reminder and he will no longer come to [forget and] stoke the coals.
Heating precooked foods on Shabbos which contain congealed fat and oil:
However the above allowance to heat up pre-baked foods only apply when [the food] does not contain fat, however bourekas which are filled with pieces of congealed fat (called Infanda) is forbidden to be heated up even at a distance from the fire in a place where [the food will] not [be able to get heated top the point of] Yad Soledes.
Melting fat in the sun: [Furthermore] [it is] even [forbidden] to leave it in the sun.
The reason for the above restriction is: because the congealed fat that is inside [the pastry] melts [in the heat] and doing so is similar to [one] crushing a piece of ice in order to liquefy it, in which case the Sages prohibited [one from doing so.] [Their reason is] being that [through doing so] one is creating [a new substance] on Shabbos which is similar to a [Biblically] forbidden action being that he is creating this water [from the ice] as will be explained in chapter 320 [Halacha 16] and this same decree applies as well to dissolving fat.
If the fat melted on Shabbos it may not be eaten: Furthermore, if [the fat] already [melted] then the fat that had melted on Shabbos is forbidden [to be eaten].
The reason for this is: as this is the law with juice that has flowed on Shabbos from fruits that are designated to be used for juice, in which [the ruling is that they] are forbidden [to be drunk]. [This is] due to a decree that [if this were to be allowed] one may come to squeeze the fruits on Shabbos [in order to make juice] being that these [fruits] are designated for this purpose as will be explained there [in chapter 320 Halacha 3]. This [suspicion] likewise applies to this fat [that has melted on Shabbos] as since it is common for [the fat] to be liquidly and transparent therefore when it is congealed it is similar to fruits that are designated to be juiced, of which [the ruling is that the juice] which flows from it on Shabbos is forbidden until night [after Shabbos].
The law if the fat will melt into the food and will thus not be recognizable: However the above [prohibition to melt the fat] only refers to when so much fat has melted that it oozes out [of the pastry], and is its own substance, [meaning] that it is not mixed into any other food and is [thus] recognizable on its own. However if it has been left such a great distance [from the fire] that not enough fat will melt for it to be oozing out [of the pastry], and rather only a slight amount of it will melt and will get absorbed into the pastry itself and [will thus] not be visible on its own, then it is allowed to [be placed near heat] even initially just like it is allowed to place a piece of ice in a cup of wine despite that the ice will melt in into it being that [the melted water] will get mixed and nullified within the wine in the cup, and is [thus] not a separate substance as will be explained there [in Chapter 320 Halacha 16].
[Furthermore] even if a small amount of [the fat] does flow out [of the pastry] and is [recognizable as] a substance of its own, [nevertheless] since it is a small amount it is not given any [Halachic] importance and is permitted.
Heating up fatty meat: Therefore it is allowed to heat up on Shabbos a piece of fatty meat even though some of [its fat] will flow being that [what will flow] is [only] a small amount [of fat].
Heating up soup or stew: However it is forbidden to heat up a pot [of stew or soup], which its fat has congealed, even by an area that [it will] not [reach] Yad Soledes, even if there is a lot of gravy inside [the pot] and the fat will thus dissolve into the gravy, as nevertheless the fat will float on its surface and be [recognizable as a] separate substance.
Other opinions: However there are opinions which argue on all this and say that there is no prohibition at all in melting fat through placing it in a hot area, as the [Sages] only prohibited breaking [and thus dissolving] a piece of ice with ones hands, however to let it dissolve on its own there is no decree [against doing so].
Therefore [according to their opinion] it is allowed to heat up this pastry which is filled with fat even in an area which [the pastry will become] Yad Soledes being that there is no cooking [prohibition involved here]. [There is] no [prohibition involved in heating] the bread because there is no [prohibition to] bake a pre-baked [food]. [Likewise there is] no [prohibition involved in heating the] fat which is congealed and dissolves because there is no [prohibition to] cook a pre-cooked [food] that is dry, even though it will melt through this second cooking as was explained above [in Halacha 11].
However a pot [of soup or stew] which its fat has congealed may only be heated in an area that the food will not be able to reach Yad Soledes being that by liquid that has become cold there is a cooking [prohibition involved in reheating it to Yad Soledes, as explained above [in Halacha 9].
The Final Ruling: Concerning the final ruling the custom is to initially be stringent like the first opinion although once the fat has already melted one may be lenient like the second opinion [to allow it to be eaten]. [Furthermore] even initially one may rely on the second opinion in a time of need, being that this is the main Halachic opinion.
Placing the fat on top of a heater that is not yet lit: As well one may be lenient to place pastries filled with fat onto a heater before it is lit and when the gentile will light it will then also heat up.
The reason for this is: because [in this scenario] even regarding the cooking prohibition, [meaning if one were to place there] a food which has a cooking prohibition applicable to it, then [cooking it] would not contain a Biblical prohibition but rather only a Rabbinical [prohibition] if he places it there prior to the gentile lighting the fire of the oven as explained in chapter 253 Halacha 27], thus here since there are opinions which completely permit [one to place even near an active fire] one may at the very least be lenient regarding placing it there before the oven is lit.
Doing it through a gentile, and not in front of an ignoramus: Nevertheless one should not be lenient in front of an uneducated Jew, and one should do so through a gentile.
Melting congealed fat on top of legumes: According to all opinions it is permitted to place melted fat that has congealed on top of different types of hot legumes and flours as long as one does not break [the fat] apart with ones hands, and rather simply places [the fat] on top of them or into them letting it melt on its own, being that [the fat] that melts is not [recognizable as] its own substance and rather becomes absorbed within the food.
Melting congealed fat on top of a hot roast: However it is questionable whether one may place congealed fat on top of hot roast in order for it to dissolve on its own, as since the melted fat does not get absorbed into the meat but rather floats on its surface it therefore can be compared to a pot [of soup or stew] which its fat has congealed of which the custom is to be initially stringent.
Precooked foods which dissolve upon re-cooking:
Although there is no prohibition to cook a precooked food that is dry, nevertheless if some of it dissolves through the cooking then it contains a cooking prohibition in dissolving the moisture if it reaches the heat of Yad Soledes.
Heating chicken and meat that has gravy: Therefore one must be very careful not to heat up roasted or cooked meat or chicken if their gravy which melts from within them will reach a heat of Yad Soledes, due to a Sekilah and Kares prohibition, Heaven Forbid.
Sugar: As well one may not pour from a Keli Rishon that is Yad Soledes onto sugar, as being that the sugar dissolves it contains a cooking prohibition.
Salt: Therefore one may not be lenient regarding our salt that although it is previously cooked, nevertheless since it dissolves upon re-cooking one may not be lenient with it any more then the salt of the old days [which was not previously cooked] based on the difference of opinions mentioned in Shulchan Aruch of which there are opinions which hold that it is forbidden to even place it in a Keli Sheiyni that is Yad Soledes, and one who is stringent is to be blessed.
Placing cold liquids on top of a kettle
Is hot enough to make food Yad Soledes: It is forbidden to place cold [liquid] on top of a kettle even in order to just warm it up [as opposed to making it hot] so long as its hot water is so hot that if the cold [liquid] were to be left on top of it for a long time then it would be able to cook, which means that it would become Yad Soledes, as the law of placing [food] on top of a kettle is the same law as that of placing [food] near a bonfire.
Is not hot enough to make food Yad Soledes: However if [the water in the kettle] is not so hot [to the point that it can warm up the food to Yad Soledes] then it is allowed.
Mixing a pot of hot food and removing its content
Not fully cooked-may not remove while hot : A pan and pot [of food] which were removed in a hot state from on the fire, if their [content] is not completely cooked one may not remove food from them with a spoon being that by doing so one mixes and [helps further the cooking which thus] contains [the] cooking [prohibition] as explained above [in Halacha 10].
Fully cooked: However if its [content is] fully cooked then it is permitted to stir it after taking it off the fire.
Stirring wool in a dyers pot: However wool that [was placed] in a large pot [for dying], even if it already received the coloring [of the dye], it is forbidden to stir it (due to [a] dying [prohibition]) as it is common practice for the dyers to consistently stir the pot in order so it not scorch.
Other Opinions: [However] there are opinions which are strict [even] regarding [stirring] a pot [of hot food] in all cases [even if the food is fully cooked].
The Final Ruling: The main Halachic opinion is like the first opinion, and one who wants to be stringent should [only] do so regarding actually stirring [the food] however regarding taking out the [food] with a spoon one should not be stringent at all if [the food] is fully cooked and is not on the fire.
Placing garlic and oil on a hot roast
It is forbidden to spread oil and garlic on a [piece of] roast while it is still hot to the point of Yad Soledes, even if it had been roasted from before Shabbos, as nevertheless [this will cause] the oil and garlic to cook.
However congealed fat does not contain a cooking prohibition [in melting it over the hot roast] although it is questionable [whether it is allowed] due to a different [prohibition] as explained above [in Halacha 28].
 Regarding Rabbinical actions, see Q&A below.
 There it explains that one is allowed to eat raw meat without removing its blood being that the blood prohibition only applies to blood that has left the flesh of the animal. Nevertheless one is still obligated to wash the meat prior to eating being that there is blood that has separated on its surface.
 Meaning he may come to add an extra piece of meat to the pot that he is cooking for the ill person in order so he too can have a piece, in which case he has done a Biblical prohibited action of cooking. Thus the Sages decree against him eating at all from any of the cooked meat even if it was cooked solely for the ill person.
 27 grams.
 This follows the ruling of the Taz in Yorah Deah 113/15, and so rules also Beir Heiytiv [there 19] and other Achronim. To note that the Beir Heiytiv mentions that it should be forbidden even for the sick person after Shabbos, however from Admur it is implied that for him it is still allowed for the sick person. However the Rama [Yorah Deah 113 Halacha 16] and Shach [in Nekudos Hakesef there in 113] Mishneh Berurah [318/14] and Gra rule that it is permitted to be eaten by a healthy person even when cooked, as since it was done permissibly the Sages never made a decree here of “cooked foods of Gentiles”.
 Vetzaruch Iyun why this is not prohibited to be moved do to that one may come to pick extra fruit on his own behalf, as said in Halacha 5. However regarding why it should not be prohibited the same way we prohibit fruit [even fully ripened] that was cut by a gentile on Shabbos [chapter 325 Halacha 8], perhaps is because the decree of it falling off on its own does not apply when a Jew took it off.
 Approximately 110 Fahrenheit. The amount of heat that one would remove his hand from there upon touching.
 This is the opinion of the Michaber. According to this opinion even if the water is still Yad Soledes but had been placed into a Keli Sheiyni, it is prohibited to further heat it. [Peri Megadim, brought in Biur Halacha. Shabbos Kehalacha p. 139]
 There it is explained that it may not be initially placed literally on the coals or even very close to the coals, rather it must be at a slight distance.
 Rashba/Ran/Magid Mishneh
 Vetzaruch Iyun as there the Alter Rebbe rules in parentheses that even if a Jew himself heats up liquid food it is allowed to be eaten being that there are opinions which permit this even initially.
 This follows the ruling of the Magen Avraham which argues on the Levush which holds that it is forbidden when it dissolves.
 A vessel that contains food that was poured into it from a pot which was on the fire,
 So rules Magen Avraham
 Taz 14
 So rules also Aruch Hashulchan 44. However the Mishneh Berurah [45 ] rules stringently by onions and garlic to not allow them to be placed in a Keli Sheiyni. So rules also Igros Moshe [4/74]
 Little Tunny is a small  It appears that the reason that this opinion is brought here and not in the previous Halacha is because in truth there is no ramification in the cases discussed in the previous Halacha as either way it is Rabbinically forbidden to place uncooked foods in a Keli Sheiyni. However here when discussing placing a pre roasted or baked food into a Keli Sheiyni this opinion needs to be brought up being that otherwise there is room to rule that placing it in a Keli Sheiyni, which is only a Rabbinical prohibition should be allowed here being that there is a dispute as to whether there is cooking after roasting, and following the rule that by a doubt in a Rabbinical prohibition we are lenient. However once this latter opinion has been brought then the idea of a Keli Sheiyni is as well a Biblical prohibition, and thus this doubt is now a doubt in a Biblical prohibition of which the rule is that one is to be stringent, as rules Admur as the final Halacha. However see next note.
 The reason for the leniency by liquids is because since the liquids mix well with the food in the Keli Sheiyni it therefore does not appear like cooking, and rather appears like one is simply cooling off the Keli Sheiyni. [Peri Megadim AA 32] As well we must say that the Sages received tradition that liquids definitely do not cook in a Keli Sheiyni.
 Q. What novelty is being said here after having already ruled above that one is to be stringent by roasted meat. Furthermore why does Admur here mention that it is a custom while above ruled that one must be stringent? Furthermore why didn’t Admur bring this latter opinion prior to stating the final ruling that it said above. Vetzaruch Iyun. To note that the Chidushim and Biurim Kolel Tzemach Tzedek learn that the previous “final ruling” was all in accordance to the stringent opinion, while here is the actual final ruling, and according to this only by bread are we stringent due to concerns of cooking as opposed to other foods and it is due to this also that onions are allowed to be placed in a Keli Sheiyni being that we do not accept the stringent opinion for all foods.
 Tzaruch Iyun on the novelty in this additional statement.
 Vetzaruch Iyun as there the Alter Rebbe in 257 Halacha 10 rules explicitly that if the coals have not been swept then it is forbidden to insulate it over the Kirah. Perhaps though here the Alter Rebbe does not mean literally that it was insulated in clothing and the like, but that it was insulated-retained its heat- by placing the bare pot on the Kirah.
 Meaning that either the food has already been cooked to the point of Ben Drusaiy, or that it contains raw meat placed right before Shabbos.
 Lit. good
 However the M”B  rules that once the Keli Rishon is no longer Yad Soledes then one may place any food in it [that does not contain a Molid prohibition].
 Such as blocks of salt that can be found in the dead sea and in other areas around the world. However salts, including sea salt, that is abstracted through evaporating water which thus cooks the water in the process is discussed in the next Halacha.
 This refers to when non-kosher food in Keli Sheiyni had Kosher food placed inside it or vice versa, in which case there are opinions that hold that the entire Kosher food is forbidden [Taz and Rashal in Yorah Deah Chapter 105] while others hold that that the outer layer of it is forbidden. [Michaber/Rama/Shach in chapter 105 in their Lechatchilah opinion].
 Meaning although they hold that it can give and receive taste, nevertheless they are all in agreement that it does not have the ability to actually cook.
 According to this reasoning any Keli Sheiyni which is very hot has the same status as a Keli Rishon. So rules Tzemach Tzedek as explained in Ketzos Hashulchan 124 footnote 31. [To note that Rav Farkash writes merely that it is proper to be stringent in this [Shabbos Kehalacha 1/38 and 2/4] while from Tzemach Tzedek and Ketzos Hashulchan it is evident that this is the way they rule.]The M”B also explains this to be the reasoning behind the bath prohibition. However other Poskim [Machatzis Hashekel, based on Rashi] learn that the bath tub case is an exception and was only made forbidden due to a decree that one may come to heat up also in a Keli Rishon. [Shabbos Kehalacha p. 66]
 This follows the ruling of the Rama. However according to the Beis Yosef/Sefaradim it is forbidden in all cases to pour cold water into a Keli Rishon.
 There it is explained that there is no insulation prohibition to insulate an item that is cold in order to thaw down its coldness. However to add heat in it is forbidden.
 A boreka is a baked or fried filled pastry.
 This opinion is based on the opinion of the Levush, of which likewise rules the Taz, as opposed to the opinion of the Magen Avraham, as was ruled above in Shulchan Aruch Halacha 25, which argues on the Levush and holds that a solid which dissolves is viewed as a solid and not as a liquid. The Mishneh Berurah rules like the Magen Avraham although concludes that it is proper to avoid placing the food in a Keli Rishon or pouring onto it from a Keli Rishon. So rules SS”K and Kitzur SHU”A. However regarding a Keli Sheiyni they are lenient if the food has been previously cooked. See Q&A by Keli Sheiyni for the ruling according to Admur. Regarding butter: According to all opinions it has a cooking prohibition even if previously cooked. [So rules Rav SZ”A. Shabbos Kehalacha p. 143]
 However the M”B 71 rules that it is permitted to place sugar into a Keli Rishon although it is proper to Lechatchilah beware from placing or pouring on it from a Keli Rishon.
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