May one begin a Melacha before Shabbos if it will continue into Shabbos?
The rule: It is permitted for one to begin a Melacha on Erev Shabbos, up until sunset, even if it will not be completed before sunset, and will thus consequently finish on its own on Shabbos. Furthermore, even if one sets up a situation that the Melacha does not even begin on Erev Shabbos, and rather the entire Melacha is done on Shabbos on its own, it is nevertheless permitted to be arranged on Erev Shabbos. The above allowance applies even if a Jew’s vessel will be doing the Melacha on Shabbos being that there is no obligation for one to prevent his vessels from doing work on their own on Shabbos.
- Noise making Melachas: In a place where there is no accepted custom otherwise, one is to be stringent to forbid starting any Melacha on Erev Shabbos that will continue into Shabbos, if the Melacha will be generating noise on Shabbos. However in a case of loss one may be lenient to begin doing even a noise making Melacha on Erev Shabbos. If the item making the noise does not belong to a Jew, even if the Melacha is being done is on behalf of the Jew, it is permitted to be started on Erev Shabbos even when no loss is involved. Likewise if it is known fact to the public that a certain activity is always begun the day before its noise is heard, even when heard during the week, then it may be done on Erev Shabbos even if it makes noise on Shabbos.
- Placing uncooked food on the fire from before Shabbos into Shabbos: Is forbidden due to the Shehiyah restrictions. See “The Laws of Shabbos” Vol. 1 “The Laws of Shehiyah”!
- Placing a vessel of water near a candle to catch its sparks: It is forbidden on Erev Shabbos to place a vessel containing water under a candle in order for it to catch the sparks of the candle on Shabbos. Likewise it is forbidden on Erev Shabbos to place water under a wax candle in order to extinguish the flame when it reaches the water level. It is however permitted to place water in an oil candle in order to elevate the oil. Furthermore the custom is to be lenient to allow one to place water under the oil even if he intends to extinguish the wick, to prevent the flame from damaging the glass of the vessel.
Examples of cases:
- Dyes: One may soak dye, herbs and barley in a bucket of water, near the onset of Shabbos, and have them remain there the entire Shabbos.
- Incense: One may place fragrance under clothing over coals close to sunset, consequently having it give off fragrance into the clothing throughout the entire Shabbos. [However to place plain fragrance over coals, having it give off good smell throughout Shabbos, is forbidden due to suspicion that one may come to stoke the coals. ]
- Traps: One may set up an animal trap on Erev Shabbos for it to trap animals on Shabbos.
- Dying wool: One may leave wool in a sealed pot of boiling dye which is off the fire in order so the wool absorb the dye throughout the entire Shabbos.
- Sprinklers: One may turn on his sprinklers before Shabbos, having them hose his garden throughout the entire Shabbos.
- Medicine:  One may place a medicinal bandage, or any other medical item, on a wound before Shabbos even though it will continue curing the wound throughout Shabbos.
- Alarm Clock: One may set up an alarm clock on Erev Shabbos, having it detonate on Shabbos.
Summary-Doing Shabbos prohibited work on Erev Shabbos which will continue into Shabbos:
It is permitted to begin a Shabbos prohibited activity on Erev Shabbos even if this activity will continue into Shabbos. This is with exception to:
- One may not place food to cook on Erev Shabbos if it will only become half cooked after the entrance of Shabbos as is explained in Vol. 1 “The Laws of Shehiyah”.
- One is to be stringent not to arrange before Shabbos that a Melacha which generates noise be activated on Shabbos, being people will suspect that the Melacha was done on Shabbos. In any of the following cases however even a noise generating Melacha remains permitted to be arranged on Erev Shabbos:
- It is known that this type of activity is always set up the day before.
- The noise making object is not known to be owned by a Jew.
- A case of loss:Being that there are opinions which say that in all cases it is permitted to set up even noise making Melachas, therefore if one will incur a loss by being stringent in the above, he may be lenient like these opinions.
- A community which has an accepted custom to be lenient may do so.
May one light incense before Shabbos having its smell burn on Shabbos? 
No as we suspect that one may come to stoke the flame.
May one place water under his candles to prevent the possibility of a fire occurring on Shabbos?
If there is suspicion of danger then one may place water before Shabbos near the candles in a way that if the candle were to fall it would extinguish. If however there is no fear of danger it is forbidden to do so.
May one close the water of his sprinklers on Shabbos?
Yes. However if one is only closing an individual sprinkler while leaving other sprinklers on, then one must verify that doing so will not cause an increase in water pressure to come out from the other sprinklers. There are opinions however which do not allow this to be done even in such a case.
May one arrange for his sprinklers to go off on Shabbos?
May one place clothing in the washing machine or dryer before Shabbos, having them be washed or dried into Shabbos?
No, as the washing machine and dryer generates noise. If however it is a case of great need, such as one is traveling on Motzei Shabbos, then one may be lenient to do so. Nevertheless even in such a case one may not make use of these clothes on Shabbos.
May one arrange that his Shabbos clock turn on a radio, television, or tape on Shabbos?
The Halachic aspects involved in doing so is discussed amongst Poskim. [see footnote] In any event it is a widespread custom to forbid doing so, as regardless of the Halachic discussion, doing so breaks the Shabbos spirit. However in a time of great need such as in times of natural disasters or war in which case one must hear news directives, one may certainly be lenient to do so, [leaving the radio on a low volume].
May one leave a radio, television, or tape on into Shabbos?
This follows the same ruling as the previous Q&A.
May one listen to the radio of a neighbor which is on?
If the neighbor is Jewish or the radio broadcast is being done by a Jew then it is forbidden to listen as one is benefiting from the Melacha done by the Jew on Shabbos. If however it is a gentile neighbor and the show is broadcasted by gentiles it is permitted from the letter of the law to listen, although it is best to avoid doing so being it breaks the spirit of Shabbos.
So long as the actual call is automated, as opposed to having an actual receptionist calling, then it is allowed. However in such a case one is to make reminders as a precaution that he not lift up the phone to answer it in the midst of awakening.
May one set up a recorder from before Shabbos to record on Shabbos?
May one leave a microphone on into Shabbos and use it?
No. Doing so is a sever prohibition.
May one leave his answering machine active on Shabbos?
For commercial use: Some Poskim rule that it is permitted to leave an answering machine on for clients and customers to leave messages and receive information. Others however forbid doing so due to a variety of factors. If majority of one’s clients or customers are Jews, then it is forbidden to leave on the answering machine according to all.
For home use: It is permitted according to all opinions for one to leave his answering machine active on Shabbos.
Voicemail: The above discussion refers to landline answering machines. However electronic voicemail systems which are provided by phone companies are permitted according to all to be left active on Shabbos, especially if one is merely leaving a recorded message of the business opening hours. However according to the above Poskim which are stringent it would be forbidden to leave a recording on the voicemail referring the clients to a gentile worker of the business.
May one leave his fax machine active on Shabbos?
This follows the same ruling as does an answering machine which was explained in the previous question. Thus in accordance to the stringent opinion one is to unplug the machine before Shabbos. In the event that a fax arrived on Shabbos it is forbidden to be read on Shabbos.
May one set up a timer to activate machines which work on electricity?
May one set up a timer to activate or shut off his lights at home?
May one set up a timer to activate a fan or air conditioner?
May one on Erev Shabbos place food on his electric plate which is not yet on but will later turn on with the timer?
If the food is not fully cooked, or is but contains liquid and has fully cooled down, it is forbidden.
If the food is fully cooked but the electric plate is not covered: Then if the electric plate has more than one heat setting and is not covered, it is forbidden to place food there before Shabbos if the food is cold. However if the food is still hot, there is a dispute amongst Poskim and it is proper to be stringent.
Food is fully cooked and electric plate is covered: If the electric plate is covered, or has only one setting it is allowed to place on it before Shabbos fully cooked food [which will still be warm by the time the clock turns on if the food contains liquid].
Practically, due to the above one may not leave a boiler attached to the Shabbos clock being that by the time the clock turns back on, the water has completely cooled off and will become re-cooked on Shabbos.
 Melacha is the general term used for all activities which are forbidden to be done on Shabbos.
 Such as to spread traps on Erev Shabbos to catch wild animals, birds and fish on Shabbos. This is permitted despite the fact that the trap is what is doing the entire action of trapping on Shabbos, as the metal becomes tied and grabs the bird on Shabbos, and similarly the booby-trap which they spread [to catch] wild animals to capture them by their feet, in which when the animal touches [the trap] it jumps and traps it. [ibid]
Vetzaruch Iyun from the discussion in Poskim [Piskeiy Teshuvos 252/1; Mishneh Halachos 7/55] regarding if one may cause an entire Melacha to begin on Shabbos, being that from here it is clearly proven that one may, and so rules also Michaber.
 The Sages did not suspect that if Melacha which was done before Shabbos is allowed to continue into Shabbos one may likewise think this Melacha is permitted to be done on Shabbos itself, as the concept of not doing Melacha on Shabbos is well known. [265/8]
 It is disputed in Poskim whether or not one may place wheat in a flour mill on Erev Shabbos and have it grind the wheat on Shabbos in a way that generates noise. Some Rishonim rule [as rules Michaber 252/5 and Admur in his 1st opinion, brought as a stam], that doing so is permitted, as they hold that it is always permitted to begin a Melacha on Erev Shabbos even if it will generate noise on Shabbos. Other Rishonim however hold [as brings Rama and Admur as a Yeish Cholkim], that doing so is forbidden, as they hold that all noise generating Melachas are forbidden to be done on Erev Shabbos if they will continue into Shabbos, due to the belittling of Shabbos. Admur concludes as written above that one is to be stringent if there is no explicit custom otherwise. [ibid]
 As when the Melacha generates noise, it attracts people’s attention and causes a belittlement of Shabbos, as people may say the person began doing the Melacha on Shabbos. [ibid]
 Such as an alarm clock which is always set up the day before.
 As in such a case there is no belittling of Shabbos apparent.
 265/8; This is forbidden due to a decree that if it were allowed to do so before Shabbos then one may come to think that it is likewise permitted to do so on Shabbos, as this Shabbos prohibition is not very well known being that people think since the water is being placed before the sparks fall it should therefore be permitted. [ibid]
 265/9; The reason for this is because one has no intent to extinguish the flame but rather to raise the oil level and hence there is no reason to suspect that one may come to think that it is also allowed to set up a jar of water to catch sparks on Shabbos. Furthermore in truth the fire would extinguish regardless of the water, as the moment the oil has burnt out the fire extinguishers on its own. Hence adding the water does not proximate the extinguishing of the flame at all and there is thus no reason to suspect that one may come to think that it is also allowed to set up a jar of water to catch sparks on Shabbos.
 265/9; Meaning that one wants to prevent the wick from remaining lit while it is on the bottom of the vessel as the flame can cause damage to the vessel. The reason for this allowance is because in truth the fire would extinguish regardless of the water, as the moment the oil has burnt out the fire extinguishers on its own. Hence adding the water does not proximate the extinguishing of the flame at all and there is thus no reason to suspect that one may come to think that it is also allowed to set up a jar of water to catch sparks on Shabbos.
 Even if the fragrance is resting within a vessel this is permitted, as even though the work is being done on Shabbos with the vessel of a Jew, this is Halachicly meaningless, as a person is not commanded that his vessels rest from doing work on Shabbos on its own [consequently of an action started from before Shabbos]. [ibid]
 Based on Bach 252, brought in Kaf Hachaim 252/52. The Bach explains that when fragrance is placed under clothing we do not suspect that one will come to stoke the coals as doing so will bring up smoke which will ruin the clothes. This implies that when there are no clothing over the fragrance that doing so would indeed be forbidden due to the above suspicion. Accordingly it is also understood why the Michaber/Admur specifically mentioned this case involving clothing.
 If however the pot cover is not sealed shut then it is forbidden due to suspicion that one may remove the lid and come to stir the wool, which contains a cooking and dying prohibition. [The mixing of uncooked food within a Keli Rishon is forbidden due to the cooking prohibition, as is explained in the laws of cooking.] If however the wool is already fully cooked then mixing it only contains the dying prohibition. [ibid. and 318/30. Vetzaruch Iyun as for why in 318/30 Admur writes “dying prohibition” in parentheses.]
 If however it is on the fire, doing so is forbidden due to suspicion that one may come to higher the flame. [ibid]
Although the original Halacha in Admur is referring to digging a channel from a spring to a garden, seemingly today’s sprinklers systems would have the same law. [Piskeiy Teshuvos 252/4] However some question the comparison saying that sprinkler systems, in contrast to a channel, make noise of which the ruling is that it may not be done before Shabbos, as explained above. Vetzaruch Iyun as to the amount of noise that can be defined as problematic.
 However on Shabbos it is forbidden to medically treat oneself with exception to the cases that are explained in Vol. 2 “The laws of Medicine”.
 This applies even if one desires it to ring for the remainder of the day. [336/4] As although it is a noise making Melacha, of which one is to be stringent against doing even before Shabbos, nevertheless since it is common knowledge that alarms are set up the day before they ring, there is therefore no applicable suspicion that people may think it was set up on Shabbos which is prohibited to be done. [252/16]
 Based on Bach 252
 Elya Raba 265/10 in name of Issur Viheter 59/45; M”B 265/6; Now although the Peri Megadim 265 M.Z. 3 argues on the law stated by the Issur Viheter, and the M”B ibid concludes that one is to only be lenient in a time of need to do so through a child, nevertheless perhaps this applies only on Shabbos, although on Erev Shabbos everyone agrees that one may place water under it to prevent danger. [see Piskeiy Teshuvos 265/6 and footnote 45] To note that the Daas Torah 265 and Kaf Hachaim 365/26 does not record the stringent ruling of the Peri Megadim even regarding Shabbos.
 As one may not place water under a candle to catch its sparks. [265/8]
 Piskeiy Teshuvos 252/4
 SSH”K 42/43
 As this is similar to a case of loss in which one may be lenient.
 Some Poskim [Mahrshag 2/118; Shulchan Melachim 6/72] rule that there involves no prohibition in leaving the radio on into Shabbos, or having a timer activate it on Shabbos. However the majority of Poskim [Beis Yitzchak 2/31; Mishpitei Uziel 2/52; Rav SZ”A brought in Shearim Hametzuyanim Behalacha 80/39; Minchas Yitzchak 1/107; Igros Moshe 4/60 regarding the prohibition of having a timer do any Melacha on Shabbos] have prohibited it for various reasons. These include: 1) Listening to business related items which is forbidden; 2) playing music through the radio 3) Benefiting from hearing a Jewish talk show, of which the Jew is desecrating Shabbos; 4) It falls under the category of Melachas which make noise, similar to a flour mill, of which it is initially forbidden to arrange before Shabbos to continue into Shabbos. 5) It is belittling to Shabbos.
 Piskeiy Teshuvos 252/6
Regarding leaving the radio on for a sick person in order to calm him down, Chelkas Yaakov 1/61 rules that it is allowed while in 3/98 he retracts that ruling and forbids it.
 Har Tzevi 1/183
 Wake up service is a service offered by companies in which they call a person’s phone as a wake up reminder, in accordance to the preferred time that he gives them. The question thereby lies in whether or not one may allow on Shabbos for this phone call to be made by the service provider.
 Beir Moshe 7/56 Kuntrus “Koach Electri”
 Meaning that the service provider has an automated phone service which daily calls the customers without the need of a human to dial the numbers or do any other form of intervention.
 As this is similar to a Shabbos clock which is set to turn on electricity, which is permitted.
 Such as to cover the phone as a reminder, or before Shabbos move it to a different area.
 See Piskeiy Teshuvos 252/7
 The Beir Moshe ibid negates this issue for a number of reasons.
 Mishneh Halachos 7/55; Beir Moshe 7/77 [Electricity]; Igros Moshe 4/60
 As the actual recording is forbidden to be done on Shabbos. See the above mentioned Poskim and their reasons.
 Shaareiy Halacha Uminhag 2/167, as rule all Poskim today.
 As the speaking into the microphone itself causes a prohibition to be transgressed.
 Such as for customers to leave messages for the business, or to be told that the office is closed etc. The question involved in doing so is if this transgresses placing a stumbling block in front of a non-religious Jew who may call, as well as if this involves doing business on Shabbos.
 Beir Moshe 6/50 Kuntrus Electri
 Minchas Yitzchak 5/14; Chelkas Yaakov 3/94
 Such as: 1. Arranging for business to be done on Shabbos; 2. Perhaps a Jew may call and one causes him to desecrate Shabbos, as leaving a message causes the machine to turn on and off, as well as it writes the message on the recording tape which is like writing on Shabbos; 3. One must protest a gentile doing Melacha with a Jews items, of which in this case is the answering machine which turns on and off upon his call.
 As by voicemail the Melacha is not being done with the Jews machine or any machine for that matter. As well no extra Melacha is being done by a Jew calling the number and having the voicemail activate, as opposed to getting a busy signal. Likewise the issue of setting up business for Shabbos was only forbidden by the Minchas Yitzchak in the scenario that one leaves a message for the client to call another person to finalize the business.
 Minchas Yitzchak ibid
 Kinyan Torah 6/17
 Piskeiy Teshuvos 252 footnote 20
 Igros Moshe 4/60
 As doing so is a belittlement of the Shabbos day, even if it itself involves no transgression. The Igros Moshe likewise discusses whether this falls under the prohibition of Amirah Leakum.
 As these matters are needed for Oneg Shabbos, as well as that it has even been accepted to ask a gentile to do so prior to the times of electricity. There is thus no room to be stringent under the claim that it belittles Shabbos.
 Shabbos Kehalacha Vol. 1 pages 244-247.
This question is dealt with extensively by many different Poskim of the previous and current generation. Some, including the Munkantcher permit it entirely. Others, including the Minchas Yitzchak and Sheivet Haleivi rule that [Lechatchilah] this is completely forbidden, for the reason that it appears like belittling of Shabbos. Others, including the Chazon Ish, Igros Moshe, and Rav Shlomo Zalman Aurbauch rule that if the food is fully cooked and the flame is covered, it is allowed. The ruling here is based on this latter opinion.