A full hour Shiur on the subject!
Keeping stringencies/Chumros at the home of a host:
When one is a guest in someone else’s home for a meal, it is common to be faced with a dilemma in which partaking in certain foods being offered may compromise one’s religious observance or stringencies, and the question is raised as how one is to properly navigate the situation. On the one hand, one should not do something which may offend the host, such as refusing to eat the food on his menu. Likewise, one is required to respect the wishes of his host, in his home. On the other hand, one cannot compromise on his religion simply because others choose to be offended. The following is the Halachic ruling on this matter:
A prohibition: Any matter which is prohibited according to Jewish law, and is not a mere custom or stringency, it is forbidden to transgress even if doing so has the potential of making another feel offended. This applies even if the prohibition is only Rabbinical in nature. Obviously, one must try the utmost to perform the matter in a way of Darkei Noam and Darkei Shalom, and thus sanctify G-d’s name in the eyes of the public.
A stringency or custom: Any matter which is a mere custom or act of piety, and is permitted from the letter of the law, may be compromised on in a case that it can cause a host to be offended, and it is not possible for the custom or stringency to be done inconspicuously and go undiscovered. There is no need for Hataras Nedarim to be performed in such a case, even if this stringency has the status of a Neder. Accordingly, we find in Halacha that one is required to transgress the custom of his community, when he is found in a community which does not keep that custom, and guarding that custom in that area will cause strife and dispute, being that it is not possible to perform it inconspicuously. This however, only applies by a custom or Chumra that is not based on a Biblical or Rabbinical requirement. However, if the custom or Chumra is based on a Biblical or Rabbinical prohibition, such as that one is accustomed to follow a certain opinion in Poskim which prohibits a certain matter or a certain food, then one must keep his custom even when he is a guest in another’s home, even if the matter is a mere Chumra. Likewise, if one’s community custom is to prohibit such a food and they are not accustomed to be lenient even upon eating elsewhere, then he must avoid eating the food. In cases that one’s custom considers the food to be an actual prohibition, one may not even eat from foods that were cooked in his pots. [See Q&A for full details regarding the pots!] Likewise, if the act of piety is kept because there is even a chance of prohibition involved in doing this matter, then one is not to break his stringency. Thus, if a host asks his guest to eat or partake in a certain matter which contains no prohibition at all, and is a mere act of piety which one avoids, then one is to inconspicuously avoid this matter, and if he can’t then he is to compromise on it. If, however, there is even a chance of prohibition involved in doing this matter, then one is not obligated to listen to his host. One can simply tell the host that he does not like the food in question that is being offered. The one exception to this rule is Pas Palter, in which case one who is eating by another person who is serving Kosher bread baked by a Gentile bakery, he may partake in the bread even though in general he holds of the stringency of not eating Pas Paltar. This exception does not extend to other cases of matters which one holds to be forbidden, whether due to letter of the law or stringency. Nonetheless, in certain cases, the custom or stringency of avoiding a certain food may only have been initially accepted in one’s own home, and not when eating out by another. Thus, we find that in Reinitz, those who generally avoid eating the fat of the stomach, would nevertheless partake in foods that contain this fat in the home of one who is lenient, and they would also eat foods that were cooked in their dishes. Likewise, we find that although Chassidim were very careful to only eat meat that was slaughtered with a certain type of hewed knives [Sakinim Melutashim], nonetheless, it was permitted for them to eat by a Seudas Mitzvah of people whose meat was not slaughtered with such knives, and in all cases they could eat foods that were cooked in pots of those who ate other meats, even if the pots were Ben Yomo. One is to contact a Rav for further guidance in this matter.
When one is a guest in another’s home, he is to be careful not to offend or hurt the host by avoiding eating their food, in all cases that the food does not pose any real Kashrus concern and is a mere act of piety. The following guidelines are to be used regarding what foods one must avoid and which may be compromised on:
In all the following cases one is to avoid eating the food, or foods cooked in Ben Yomo pots, even if it may offend the host:
1. The food is Biblically or Rabbinically forbidden.
2. One suspects the food may have non-Kosher ingredients mixed in.
3. Furthermore, if one follows an opinion who rules the food is forbidden, even though there are opinions who hold it is permitted, he must avoid eating the food, or foods cooked in a Ben Yomo pot.
4. Furthermore, if one is stringent upon himself to suspect for opinions that consider the food forbidden, even though he agrees it is permitted from the letter of the law, he must avoid eating the food, or foods cooked in a Ben Yomo pot [unless he only accepted to be stringent in his own home].
5. Furthermore, even if from the letter of the law the food is permitted but one’s community custom is to prohibit such a food and they are not accustomed to be lenient even upon eating elsewhere, then he must avoid eating the food, or foods cooked in a Ben Yomo pot.
In all other cases in which the stringency is a mere act of piety and does not hold any suspicion of a Halachic prohibition and is not a community custom, one may partake in the food, if he is unable to inconspicuously avoid it.
Examples of matters which are based on prohibitions or community customs and hence are not to be compromised even when eating by a host who is lenient based on his custom or other Poskim:
1. Chalav Yisrael
2. Heter Mechira produce.
3. Gebrochts/Matzah Shruya.
4. Foods that contain a true Kashrus concern and do not have a reliable Hashgacha.
Examples of matters that may be compromised on when eating at a host if one is unable to avoid the matter inconspicuously:
1. One may eat from non-Chassidishe Shechita that contains a reliable Hashgacha.
2. One may eat from all Hashgacha’s that are reliable, even if in general one is Makpid to only eat from a certain Hashgacha in one’s home.
3. Personal Pesach Chumros and acts of piety which have no basis in Halacha or community custom may be compromised on when eating by others. [To note many avoid eating by others over Pesach in order to avoid uncomfortable circumstances that can be created due to personal Chumros. However, in the event that an invitation was accepted, the guest is to act accordingly.]
When eating by another person’s home, is it proper to question the Hashgacha’s that they use?
Some write that when eating by a person who is known to be a G-d fearing Jew who is knowledgeable of basic Kashrus laws, one is not to inquire as to the Hashgacha’s of the foods, and whether the foods were checked for insects and the like, in order not to shame the person.
May one who avoids eating a certain food eat from the pots of one who is lenient?
Pot is not Ben Yomo: If the pot that was used to cook the food is not Ben Yomo [24 hours] from use of the food in question, then one may eat food cooked in this pot. However, initially, one may not cook in these pots for himself if he holds the food in question to be forbidden from the letter of the law. If, however, he avoids eating the food due to Minhag or Chumra, then he may even initially cook in these pots that are not Ben Yomo.
Pot is Ben Yomo: If the pot that was used to cook the food is Ben Yomo [within 24 hours] from use of the food in question, then whether one may eat from foods eaten in that pot depends on the reason of avoidance. If one avoids eating a certain food due to that in his opinion the food is forbidden from the letter of the law, or due to that he follows a Posek who prohibits the food from the letter of the law, then he may not eat foods cooked in the Ben Yomo pot. If, however, he avoids eating the food due to Minhag or Chumra, then he may eat from the pots even if they are Ben Yomo, if it is known that the custom or stringency was never accepted in such a case. If, however, the custom or stringency was accepted even in such a case, then one may not eat from the foods cooked in the Ben Yomo pot.
Is a regular pot considered Ben Yomo? A typical pot is not considered Ben Yomo. However, if one is able to ask his host as to its status, then he is to do so. If, however, one is unable to ask his host, or the host is not so trustworthy, then one may assume the vessel is not Ben Yomo.
May one who only eats Chalav Yisrael, eat food cooked in the pot of one who eats Chalav Akum?
Those who do not eat Chalav Stam in America, due to them considering it not Kosher, may not eat food that was cooked in such pots if the pot was Ben Yomo at the time of cooking, unless the food contains 60x the Chalav Stam. Those that avoid eating Chalav Stam as a mere stringency are to likewise be stringent to require 60x in the food if the pot was Ben Yomo at the time of cooking. If however one cooked Chalav Yisrael milk in the pot then there is no need for them to be stringent in this matter. If Chalav Akum cheese [and not milk] was cooked in the pot then there is more room to be lenient to eat the food that was cooked in it.
 Based on: Admur 468:14; Rama Y.D. 112:15; 119:7; Shach Y.D. 112:26 and 119:20; Shaareiy Teshuvah 170:6; M”B 170:16; Piskeiy Teshuvos 170:8
 Michaber 170:5 “One who enters a home is to do everything the host instructs him”
 Admur 468:14
 Admur ibid in parentheses; Peri Chadash 496:16
 See many examples brought in our section on refusing to shake the hand of a woman, and how one is to politely avoid the situation.
 Admur 468:14; See Igros Kodesh 14:391 regarding Nussach of Davening; 5:91; 16:12 and 99; 19:249 regarding wearing a Tallis as Chazan
 Rama 568:2; 581:2 [regarding a Bris during Bahab or Aseres Yimei Teshuvah]; Shach Y.D. 214:2 that one may eat by a Seudas Mitzvah even though it breaks his Chumra which became accepted as a Neder; M”A 581:12; Machatzis Hashekel ibid; Degul Merivava ibid and Yoreh Deah 214:1 and Pischeiy Teshuvah Y.D. 214:1 that a temporary lifting of a Chumra that becomes a Neder is allowed in a case of need; Piskeiy Teshuvos 170:8; See Hearos Ubiurim Ohalei Torah 627 in which based on all above, his questions are answered, as there is no Issur of breaking a Neder in such a case.
Opinion of Michaber and Shach: The Michaber 214:1 rules regarding the Hiddur of fasting during Aseres Yimei Teshuvah, that even if one became weak, he is required to do Hataras Nedarim. The Shach 214:2 explains that the reason for this is because only those circumstances that are publicly known not to be included within the Hiddur, such as eating during a Bris Mila during Aseres Yimei Teshuvah, do not require Hataras Nedarim. However, an unexpected circumstance is included in the Hiddur and thus requires Hataras Nedarim. The Degul Merivava ibid argues against the Shach’s explanation, and says the Michaber’s ibid ruling referred to a case that due to weakness the person wanted to revoke forever his custom, and for this everyone agrees that Hatara is required.
 Admur ibid; Rebbe ibid
The reason: As the sustaining of peace is of greater importance than a custom, if the custom is not a Biblical or Rabbinical requirement. [Admur ibid] As Machlokes is a Biblical prohibition according to all. [Igros Kodesh 14:391]
 Admur ibid
 See Rama 112:15 that only by Pas Paltar do we make an exception of compromise; [See however Rama 115:3 that this exception applies also to butter and the Levush explains that this is because it is an Issur Kal; See however Taz 115:13 who negates the Levush and explains that butter is also an exception because in those areas that people eat it, they make it in a way that is Kosher without suspicion] See also Rama Y.D. 119:7 that it is forbidden for a host to feed his guest a food which the guest holds to be not Kosher from the letter of the law, or due to stringency; See Shach 119:20 and Beir Heiytiv 64:10 regarding the Chelev of the Keres that if the custom is to forbid the Cheilev then one may not even eat in the dishes of one who follows those Poskim who is Matir; See Rama 64:9 who permits eating from the pots of Bnei Reinitz and Shach 64:12 who even permits eating from their food. The Shach and Beir Heiytiv ibid explain that this Heter only applies for communities within Reinitz who are accustomed to prohibit, unlike the widespread custom to be lenient. However, those who come from a community in which everyone accepts the matter as a prohibition, then there is no leniency accorded even regarding the pots.
 Shach 119:20 and Beir Heiytiv 64:10
 Shach Y.D. 119:20
 Shaareiy Teshuvah 170:6; M”B 170:16
 Shaareiy Teshuvah 170:6; M”B 170:16; See Ashel Avraham of Butchach in Tehila Ledavid, brought in Piskeiy Teshuvos 170 footnote 40
 See Shach Y.D. 112:26; Shaareiy Teshuvah 170:6; M”B 170:16
 See Shach Y.D. 112:26
 Rama 112:15; Shach 119:20
The reason: As if one refuses to eat the bread, which is the main staple of the meal, it can cause enmity between the people. [Rama ibid; Shach 112:26]
 Rama ibid; Shach ibid; Taz 115:13
 See Rama 64:9 who permits eating from the pots of Bnei Reinitz and Shach 64:12 who even permits eating from their food. The Shach and Beir Heiytiv ibid explain that this Heter only applies for communities within Reinitz who are accustomed to prohibit, unlike the widespread custom to be lenient. However, those who come from a community in which everyone accepts the matter as a prohibition, then there is no leniency accorded even regarding the pots.
 Letter of Admur printed in Beis Rebbe “Heaven Forfend to separate from the Seudas Mitzvah of one’s area and consider them to be eating not Kosher meat”
 Letter of Admur in Beis Rebbe regarding a Seudas Mitzvah; See Ashel Avraham of Butchach in Tehila Ledavid, brought in Piskeiy Teshuvos 170 footnote 40
 Piskeiy Teshuvos 170:8
 Piskeiy Teshuvos 170 footnote 40
 Shach Y.D. 119:20; Beir Heiytiv Y.D. 64:10
 See Shach ibid that in general we say “They were not stringent to this extent to even forbid the vessels that are not Ben Yomo.”
 Shach ibid based on Teshuvas Mahralbach 121; Beir Heiytiv ibid based on Peri Chadash
 See Shach and Beir Heiytiv ibid regarding Bnei Reinitz; Admur 453:5 regarding Kitniyus that it is Batul Berov being it is a mere stringency; Letter of Admur in Beis Rebbe regarding eating foods cooked in pots of people who used non-Melutash knives for slaughtering.
 See Shach and Beir Heiytiv ibid regarding Bnei Polin
 Based on Admur M”A 489:17; 489:29; Darkei Teshuvah 98:53 in name of Beir Oshek; Nodah Beyehuda; Daas Torah.
 As explained in Admur ibid regarding the stringency of Chadash
 As explained in Admur ibid regarding the stringency of Chadash that it is nullified in majority in Min Bemino.
 See Shach 115:17 for a dispute in whether one requires 60x or majority. Now although we rule like the Shach that 60x is required nevertheless perhaps for those that consider Chalav Yisrael in America a mere stringency, perhaps theyc na be lenient. However for those that consier it not Kosher there is certainly o room to be lenient against the Shach.