As the minutiae are great and the practicality of taking a Neder in Mishnaic Hebrew is not, it may be too confusing to attempt translating accurately into English. Hence, many specific cases and their discussions have been omitted.
There are a number of types of Nedarim: Nidrei Mitzvah or Nidrei Mitzvah obligate one to perform a Mitzvah or provide Tzedaka, and Nidrei Issur prohibit one from engaging in optional activities.
Precautions and Circumstances for Taking Nedarim
- One should not regularly take a Neder: even if he fulfills it, he is called a Rasha and sinner. If he has a Petach to annul Nidrei Issur with Hatarat Nedarim and doesn't, he's considered a Rasha, but one should avoid annulling Nidrei Mitzvah. Rather, one should strive to fulfill them, as, once Nidrei Mitzvah have been taken, it's a Mitzvah to fulfill them.
- If one delays fulfilling a Neder, his account is "opened" in Heaven.
- Taking a Neder is equivalent to building a Bamah at a time in which doing so is prohibited, and following through with it is equivalent to bringing a Korban on that Bamah. Instead, it's better he have it annulled. This is only true, however, with respect to regular Nedarim. It's actually a Mitzvah to fulfill Nidrei Hekdesh, and one should only attempt to annull them in very drastic situation.
- At the same time, one shouldn't have Nedarim rolling off his lips and rely on always being able to annul them if necessary, as he will still be punished. The Ben Ish Chai likens such a person to one who throws himself into refuse and then requests that others bathe him. The Acharonim actually recommend one who seeks annulment of Nedarim be penalized to discourage futher Nedarim.
- It's preferable to not even pledge Tzedaka in the form of a Neder. Rather, if he has the money, he should donate it right away. If he doesn't, it's better not to take the Neder until he does.
- If one does have to pledge with the community, he should add "Bli Neder."
- One may take a Neder in a challenging, trying time ("Et Tzarah"). It's a Mitzvah to fulfill a Neder taken Be'et Tzarah; however, it's debatable if such a Neder can be annulled. Some are only lenient in extremely difficult situations, so it's recommended one refrain from articulating it as a Neder and instead donate the money to Tzedaka at the earliest opportunity.
Nidrei Mitzvah, Minhag Tov, and General Minhagim
- Nedarim and Shevuot may be taken as means of strengthening one's religious commitment, both in terms of fulfilling positive Mitzvot and evading the violation of negative ones.
- However, one must be extremely careful when taking a Neder or Shevua in the context of Mitzvot, because even the more innocuous formulation will actually be binding.
- A vow to move to Eretz Yisrael or make a pilgrimage to the graves of Tzaddikim is a Neder Mitzvah and only subject to annulment in extreme situations.
- One who wishes to fast on Erev Rosh Chodesh, during Shovavim, or during Yamim Noraim should verbally stipulate before he begins to that he does not wish to accept this good practice as a Neder but rather to do it when he wishes and not when he doesn't. Each time he does wish to fast, he should accept the fast the day before. If he began without this stipulation and now wants to discontinue his lofty optional practice, for example, because it's too difficult, he must first perform Hatarat Nedarim. He should not regret all the Mitzvot he did until now, but rather regret accepting the practice as a Neder passively and not preceding it by saying "Bli Neder."
- Refraining from performing actions which are permitted because one incorrectly thinks they're prohibited is considered a mistaken Neder and does not require Hatarat Nedarim to permit. Even if one thought it was a grave sin and then discovers it's merely a stringency, it is not considered a Neder
- A person who took upon himself to learn daf yomi and wants to stop needs to do hatarat nedarim. But if he wants to switch to learn halacha instead of daf yomi, some hold that he does not need hatarat nedarim.
- Nedarim Siyag LePrishut: Taking a Neder to adjust one's personal attributes and tendencies is a form of serving Hashem. Examples include controlling one's extravagant appetite for meat and wine by taking a Neder against eating them for a period of time. Similarly, forbidding oneself from general indulgences is a means of bringing oneself to lesser focus on materialism. Nevertheless, one shouldn't become accustomed to taking Nidrei Issur (Prohibitive Nedarim). Instead, one should abstain from the actions and entities that he wishes to abstain from but without taking a Neder in the first place.
- Unlike Shevuot, which take effect on the person, Nedarim take effect on the object, therefore, a one can take a Neder to not perform a Mitzvah but not a Shevuah. The Jewish People are "Mushbaim veOmdim MeHar Sinai" previously under oath at Sinai to perform the Mitzvot, and a Shevuah cannot negate another Shevuah. One who takes such a Shevuah is subject to Malkot, as it's a Shevuat Shav. At the same time, if one took a general Shevuah that prohibited more than just this Mitzvah, it would take effect.
The Absence of Innumerable Specific Examples
- There are many complicated minutia discussed in the Talmud and its commentaries regarding specific formulations of Nedarim, but they don't make it to the page of Shulchan Aruch for practical reasons. Even those that do appear in Shulchan Aruch may not be relevant, as בנדרים הולכים אחר לשון בני אדם - we follow the common jargon when it comes to understanding Nedarim, so many of the cases no longer apply.
- Additionally, we follow the understood intention of the one taking the Neder than solely following his words, when he takes a Neder relevant solely to himself.
Ikar HaNeder & Hatfasah BaDavar HaNadur
- The essential form of a Neder entails declaring that a permitted object be prohibited and be associated with an object which itself is the product of a previous vow (Davar HaNadur). For example, "This loaf of bread should be prohibited to me like a Korban," because a Korban is an inherently permitted animal that is sanctified via a Neder.
- Similarly, if one already prohibited an object upon himself, he can then subsequently prohibit another object by associating it with this one. For example, "This loaf of bread should be prohibited to me like that one (which he already prohibited via a Neder)." 
- The associated object need not be a Korban, but, rather, it can be anything that is sanctified with one's speech.
- The efficacy of absence of association (i.e. only saying "This should be prohibited to whomever") in a Neder leaves it unclear if the Neder will be Chal, but we apply the axiom of Safek DeOraita LeChuma and assume it is.
- If one hears his fellow declare a Neder and then himself says "And me like you!" within Toch Kedei Dibbur, he creates a bona fide Neder. This is true even if a hundred people follow, one at a time, each within Toch Kedei Dibbur of the last.
Hatfasah baDavar HaAssur (Inherently Prohibited Objects)
- If one associated the object with an object that is inherently prohibited, such as a non Kosher animal or idol (Hatfasah baDavar HaAssur), the Neder is not binding on a Torah level. For example, declaring that "This meat should be prohibited unto me like pig meat" is ineffective.
- Some argue that, on a rabbinic level, any such a Neder with association to an inherently prohibited object is effective on an Am HaAretz. Additionally, basic Charatah would be insufficient, and he would instead require a Petach from a different approach (MiMakom Acher) to annul it. Many others, however, argue that this stringency by Am HaAretz only applies when his ineffective Neder is taken to prohibit his wife unto him. This opinion also claims that, nowadays, everyone has the status of Am HaAretz.
- The Chachamim did not impose their penalty in a case in which one was forced to take a Neder against his wife, and he associated her with an inherently prohibited object.
- Granted an individual cannot declare his wine as "Yayin Nesech" or "Pat Akum" through a standard Neder, if he did it as a penalty to others for violating a stipulation he made, some claim it's effective, while others disagree.
- A community can take punitive measures against members who act inappropriately and prohibit the objects of such individuals on others.
- In order for a Neder to take effect, one must verbalize is with his mouth and mean it with his heart. Therefore, if he targets the wrong item with his words, such as by specifying barley when he really meant wheat, the Neder has no effect.
- Signing a contract that has a Neder or Shevuah written on it that was not also verbally articulate is probably ineffective, but some recommend being stringent, and that's how the Ben Ish Chai rules.
Ambiguous Formulations and Stam Nedarim LeHachmir
- If one makes an ambiguous association to an item, such that his words can be interpreted in one of two ways, either as a Davar HaNadur or as a Davar HaAssur, the axiom of "Stam Nedarim LeHachmir" dictates that we assume he meant the Davar HaNadur. Therefore, if he assoiated his Neder with Maaser, without specifying whether he meant Maaser Rishon (a Davar HaAssur) or Maaser Behemah (a Davar HaNadur), the Halacha assumes by default that he meant the latter, and his Neder is effective.
- However, if he clarifies his intention as being the Davar HaAssur, he is believed and doesn't even need She'elah on his Neder, even if he's an Am HaAretz.
- At the same time, if most inhabitants of the community understand the ambiguous unspecified language to refer only to the Davar HaNadur, then he is not believed if he claims that he really intended for the Davar HaAssur. As such, one who associates his Neder with Terumah, which can mean either Terumat of produce given to Kohanim, a Davar HaAssur, or Terumat HaLishkah (donations to the Beit HaMikdash), a Davar HaNadur, and doesn't specify which one he had in mind, is bound by his Neder. If he does specify in either direction, he is believed, but, if most people in his area refer to Terumat HaLishkah as Terumah, even if he claims he meant Terumah of produce, the Neder is binding and he is not believed against the local parlance. Some say that a Talmid Chacham is believed against the majority, while others distinguish between this case and other ones.
- The gravity in deciding ambiguous references based on the majority of the community also works to be lenient against the one taking the Neder. For instance, if one associated his Neder with Yayin Nesech, which can refer to either Yayin Nesech that is brought on the Mizbeach with certain Korbanot in the Beit HaMidkash or to Yayin Nesech used in Avodah Zarah worship, it takes doesn't take effect, even if he follows up by claiming he had the former in mind.
Unintuitive Elucidations of One's Formulation (Perusham LeHakel)
- One who takes a Neder that intuitively would be interpreted one way ("I prohibit myself from my wife" intuitively means the woman he's currently married to) but then follows up and elaborates that he actually intended to refer to something that is a valid interpretation of his words but completely unintuitive given a lack of context ("I meant my first wife whom I already divorced.") is believed if he's a Talmid Chacham, but not if he's an Am HaAretz, in order to prevent making light of Nedarim. Although, an Am HaAretz would only require Charatah and not a Petach.
- If an Am HaAretz did this and subsequently violated his Neder, although we penalize one who violates a Neder MiDeoraita by making him endure a period of time without violating his Neder equal to the interval of time over which he did violate it, we do not penalize him in this situation, since it is only a Neder MiDerabbanan.
- For Ashkenazim nowadays, everyone has the status of Am HaAretz.
- An incompletely formulated Neder, otherwise known as a Yad, can take effect just as a regular Neder does or it can not, depending on the level of ambiguity. If one's intention is mostly apparent (ידים מוכיחות), it is a valid Neder. That is to say, that if one says "I vow from you that I won't eat from you," (מודרני ממך שאיני אוכל לך) without saying "prohibited" or "Korban," it is nevertheless valid.
- If the formulation is further lacking (ידים שאינן מוכיחות), i.e. it can be interpreted in more than one way, then some hold that we default to the most apparent interpretation, while others say the entire Neder is invalid.
- If the formulation lacks any implication of a neder altogether, such as saying "That I won't ) it is not valid .
- "I vow to you from eating and benefiting." (מודרני לך מאכילה או מהנאה) creates a Neder prohibiting eating and benefiting both ways between the one who took the vow and the one to whom he said it.
- "I vow from you from eating and benefiting." (מודרני ממך...) only creates a one way prohibition on the one who took the vow receiving benefit from the one he said it to.
- Due to the fact that wicked people are more oft to take Nedarim, one who takes a Neder "Like the vows of the wicked, this should be assur to me," (נדרי רשעים) it would be effective. Inversely, Tzaddikim never take Nedarim, so a Neder formulated on "Like the vows of Tzaddikim" (כנדרי צדיקים), would not be effective. However, Tzaddikim do volunteer Mitzvot, so a Neder formulated on "Nidvot Tzaddikim" (נדבות צדיקים), would be effective.
Neder Formulated as a Shevua
- A Neder fundamentally differs from a Shevua in that a Neder is a prohibition that takes effect on the item vowed upon, while a Shevua takes effect on the person. As such, the subject of a Neder must be the item at hand ("This item should be prohibited to me"), and the subject of a Shevua must be the person ("It should be prohibited for me to do this action"). If a Neder is formulated in the language of a Shevua, there's is a great debate if it takes effect at all or at least on the level of a Yad, and many opine that it is ineffective, unless it's with respect to performing a Mitzvah. Nevertheless, because it has become commonplace to take Nedarim in such a language, one should not be lenient, lest people become even more lax with Nedarim.
- Some argue that Nezirut is outside the scope of this discussion and would take effect regardless, while others disagree.
- A Neder can take effect on a preexisting Neder, Nedarim are prohibitions on the object, not on the person, unlike Shevuot. Therefore, multiple Nedarim taken on an object take effect and accordingly increase the number of prohibitions violated when the Neder is violated.
- The Torah's mandate enabling one to take upon himself a Neder, Korban, Shevua, or Nezirut is not limited to the perfect pronunciation of the keywords (Neder, Korban, Shevua, and Nazir). Even a mispronunciation would take effect, given it's common to pronounce the word that way by some people in the place one is taking the Neder. For example, "Konam" could legitimately substitute for "Korban" in the time and communities of the Talmud. Gross mispronunciations (Kinuiyei Kinuiyim), however, are not effective.
- The effectiveness of usage of the above keywords also depends on one's own understanding of them. If he doesn't understand what he's saying, his statement is invalid.
- A Neder with an unspecified time period takes effect indefinitely.
- One who dreams of himself taking a Neder or Shevuah should pursue Hatarat Nedarim by at least three, but preferably ten, people using Charatah as with any other Neder. Even if he actually annulled it in his dream, we are strict to avoid the chance that the Neder was for real and the annulment was not. The same is true for a woman; he husband cannot revoke her Neder in this case. Additionally, even if someone else had a dream that one took a Neder, one should have it annulled.
Changing One's Mind
- One may rescind his Neder within Toch Kedei Dibbur, if he does so verbally, regardless of volume, but not mentally.
Items Subject to Prohibition via Nedarim
- One can declare a Neder on an item that is not yet in existence (Davar SheLo Ba LaOlam) to be prohibited to himself once it comes into existence but not to others.
One Who Prohibits Himself From Another
- "Maddir" means one who takes the Neder to prohibit his benefit on another, and "Muddar" means one who is prohibited from receiving Hanaah.
- One can only prohibit his own possessions to himself or others or of other people's possessions to himself. Therefore, one cannot prohibit another person's belongings on his fellow.
- One who takes a Neder not to speak with his friend may still write him a letter or speak to someone else in his vicinity, even if he will hear. If he's doing it intentionally, however, even if there's a third party in between, it's not appropriate.
- On a Torah level, Shevuot can take effect on intangible object, but Nedarim can only take effect on tangible ones. Although, the latter would take effect on a DeRabbanan level; therefore, one who vows not to listen to his to his friend's prayer may not do so MiDeRabbanan. However, if he prohibited himself to his friends body, specifically, at least, his mouth, in this case, the Neder would take effect on a Torah level. The same is true for another's handiwork: only by prohibiting oneself to his fellow's hands can the Neder take effect Min HaTorah.
- Prohibiting one's Sefarim to his friend includes his friend's learning of the Sefarim, because they could have been rented to him and now he's benefiting from free usage, unlike by Mitzvah items.
Benefiting His Wife
- Everything that a woman gains possession of becomes her husband's possession, unless certain stipulations are made. One who prohibited himself to his son-in-law may give his daughter money for her own personal use, as long as he stipulates to her that it's a gift that her husband has no control over and she can do whatever general or specific action she pleases with the money. If he does not say both, even if he stipulates that the husband should have no control, his stipulation is ineffective and he causes his son-in-law to gain possession of the gift and violate the Neder. Ashkenazim are stringent if the stipulation was general and not a specific action for her to do with the money.
- If the gift is transferred in a permissible way, then the husband may benefit from it.
- Giving one's daughter food, not money, does not require any explicit stipulation.
- If one forgot if he took a Neder or if he took a Shevuah, he must act under the stringencies of both Nedarim and Shevuot. Similarly, if he isn't sure if he took a Shevuah in the first place, he must be stringent due to the uncertainty.
- Even if an external impetus brings one to fulfill his Neder, such as if he took a Neder to visit a certain town and ended up having to go there on business, his Neder has been fulfilled.
- Shulchan Aruch Yoreh Deah 203:1
- Ben Ish Chai (Shanah Shniah, Re'eh 2)
- Shulchan Aruch Yoreh Deah 203:2, Ben Ish Chai (Shanah Shniah, Re'eh 1)
- Shulchan Aruch Yoreh Deah 203:3
- Ben Ish Chai (Shanah Shniah 5)
- Shulchan Aruch Yoreh Deah 203:4, Ben Ish Chai (Shanah Shniah, Re'eh 2)
- Shulchan Aruch Yoreh Deah 203:4, Ben Ish Chai (Shanah Shniah, Re'eh 4)
- Shulchan Aruch Yoreh Deah 203:6
- Ben Ish Chai (Shanah Shniah, Re'eh 3)
- Shulchan Aruch Yoreh Deah 203:6
- Nedarim 8a, Shulchan Aruch Yoreh Deah 213:2, Shach YD 203:6. Rav Yosef Dov HaLevi Soloveitchik once went three hours overtime in his regular lecture, which was usually two hours long, on a Thursday in Yeshiva University, to the astonishment of his students. Those who remained by the time he stopped were further astounded to discover he did so because the previous week he had told the class that "Next week we will finish the chapter." and explained how that alone was enough to be considered a binding Neder. Since they didn't even finish, they had to seek out students who weren't in their class to form a Beit Din for Hatarat Nedarim. (Nefesh HaRav pg. 235)
- Ben Ish Chai (Shanah Shniah 6)
- Ben Ish Chai (Shanah Shniah, Re'eh 17)
- See Shulchan Aruch (Yoreh Deah 214) at length
- Ben Ish Chai (Shanah Shniah, Re'eh 17)
- Yechava Daat 6:52
- Shulchan Aruch Yoreh Deah 203:7, Ben Ish Chai (Shanah Shniah, Re'eh 4)
- Ben Ish Chai (Shanah Shniah, Parashat Re'eh 19)
- Shulchan Aruch Yoreh Deah 204:1, Shach Yoreh Deah 204:6
- Shulchan Aruch Yoreh Deah 217:1
- Shulchan Aruch Yoreh Deah 218:1. See commentaries at length.
- Shulchan Aruch Yoreh Deah 204:1
- Shulchan Aruch Yoreh Deah 204:1, Ben Ish Chai (Shanah Shniah 8). Language based on ArtScroll commentary to Nedarim 14a
- Shulchan Aruch Yoreh Deah 204:2
- Ben Ish Chai (Shanah Shniah 7)
- Shulchan Aruch Yoreh Deah 204:31
- Shulchan Aruch Yoreh Deah 205:1. See Chochmat Adam 92:5 and Ben Ish Chai (Shanah Shniah 9) who entertain the possibility of it being Min HaTorah depending on how it's articulated.
- Shulchan Aruch Yoreh Deah 205:1, Ben Ish Chai (Shanah Shniah 9)
- Rama Yoreh Deah 205:1. The Ran (Nedarim 13b s.v. HaOmer leIshto) explains that we're extra stringent in this respect to discourage him from taking further such Nedarim, in the chance that he would do it with association to a Davar HaNadur the next time and successfully prohibit his wife. Taz Yoreh Deah 205:2. The Perishah (Yoreh Deah 205:3) adds that we don't want him to avoid the Mitzvah of Peru uRevu. Shach Yoreh Deah 205:5.
- Shach Yoreh Deah 205:2.
- Shulchan Aruch Yoreh Deah 205:2 quotes both opinions as Yesh Osrim and Yesh Mattirim; therefore, his ruling is in the lenient direction. At the same time, the Rama posits it takes effect on a rabbinic level.
- Beit Yosef, Rama Yoreh Deah 205:2
- Ben Ish Chai (Shanah Shniah 14)
- Ben Ish Chai (Shanah Shniah 14)
- Shulchan Aruch Yoreh Deah 208:1
- Shulchan Aruch Yoreh Deah 208:1. The Bach Yoreh Deah 208 s.v. Mihu is bothered by the apparent contradiction between this case, where the Shulchan Aruch takes the position of the Rosh against the Rambam that even an Am HaAretz doesn't need She'elah, and in 205:1, where he takes the position of the Rambam that an Am HaAretz requires She'elah for any Neder associated with a Davar HaAssur. The Bach concludes in favor of the Rambam in this situation and posits that one should be stringent by an Am HaAretz here, as well. However, the Shach Yoreh Deah 208:2 distinguishes between the two instances as follows: Whereas the Am HaAretz who unknowingly took a Neder associated with a Davar HaAssur is penalized for his Halachic illiteracy, an Am HaAretz who takes an ambiguous Neder and subsequently clarifies it to be in reference to a Davar HaAssur isn't penalized, because he clearly knows that association with a Davar HaAssur is inneffective.
- Shulchan Aruch Yoreh Deah 208:1.
- Perishah Yoreh Deah 208:5 posits that the Talmid Chacham should logically be believed here if he's believed in 208:2. Shach Yoreh Deah 208:5 argues that an Am HaAretz is not believed and a Talmid Chacham is when there are one of two ways to interpret things, but when there's only one way to interpret a statement, given the parlance of the community, even a Talmid Chacham would not be granted any credence. Pitchei Teshuva Yoreh 208:2 cites the Chavot Yair Siman 15 who sides with the Perishah.
- Shach Yoreh Deah 208:4
- Shulchan Aruch Yoreh Deah 208:2
- Shulchan Aruch Yoreh Deah 208:2
- Shach Yoreh Deah 208:8. See 205:5
- Shulchan Aruch Yoreh Deah 206:1. Note that the formulation of "that I won't eat from you" (שאיני אוכל לך) is different according to some from "that which I eat from you" (שאני אוכל לך). Rama Yoreh Deah 206:1. Shach Yoreh Deah 206:2 discusses the effectiveness of only saying שאני אוכל לך, and even when leaving out שאני or לך.
- For example מרוחקני ממך could be interpreted as not receiving benefit or keeping a distance. Since the latter is more apparent, the Neder will only be effective inasmuch as he will be prohibited in entering the four Amot radius of the one he took the vow against. Rambam as quoted by Shulchan Aruch Yoreh Deah 206:1
- Rama Yoreh Deah 206:1. Though it's not printed in every edition Bach ibid 206:1, Taz ibid 206:1, and Shach ibid 206:6 point out how it's clearly missing, as indicated by his glosses to 206:3 referring back to a previous comment. See Shulchan Aruch ibid 206:3 for similar discussion exists with respect to Nidui and Shamta.
- Shulchan Aruch Yoreh Deah 206:1. See Shach Yoreh Deah 206:2 for more specific cases and their effectiveness.
- Shulchan Aruch Yoreh Deah 206:2
- Shulchan Aruch Yoreh Deah 206:2
- Shulchan Aruch Yoreh Deah 206:4
- Shulchan Aruch Yoreh Deah 206:5 as a Stam vaYesh to be lenient Min HaTorah or not. See Shach Yoreh Deah 206:9 for details with respect to parameters of formulation. The Ben Ish Chai (Shanah Shniah 5) is stringent as a means of safeguard, but Rav Ovadia (Yabia Omer vol. 8 Yoreh Deah 20:1-2) argues that we follow the Stam LeGamrei, especially because the Yesh is a minority in face of the numerous Rishonim who are lenient. He allows a woman who took a Neder beLashon Shevua to not observe it at all to protect Shalom Bayit.
- Shulchan Aruch Yoreh Deah 206:5. See Shach Yoreh Deah 206:10 and Rabbi Akiva Eiger ad loc.
- Ben Ish Chai (Shanah Shniah, Re'eh 23)
- Shulchan Aruch Yoreh Deah 207:1. See Beit Yosef and Rabbi Akiva Eiger ad loc.
- Shulchan Aruch Yoreh Deah 207:1
- Shulchan Aruch Yoreh Dea 219:3
- Ben Ish Chai (Shanah Shniah, Re'eh 15)
- Ben Ish Chai (Shanah Shniah, Re'eh 16)
- Shulchan Aruch Yoreh Deah 204:4, Ben Ish Chai (Shanah Shniah 10)
- Shulchan Aruch Yoreh Deah 225:1
- Shulchan Aruch Yoreh Deah 221:10, Shach Yoreh Deah 221:54. See R' Akiva Eiger Yoreh Deah 221:13 regarding sharing secrets with a third party to tell the person he's not supposed to share with.
- Ben Ish Chai (Shanah Shniah, Re'eh 18)
- Shulchan Aruch Yoreh Deah 221:11, Taz Yoreh Deah 221:40, Shach Yoreh Deah 221:55
- Shulchan Aruch Yoreh Deah 222:1
- Taz Yoreh Deah 222:3, Shach Yoreh Deah 222:3
- Taz Yoreh Deah 222:1
- Shulchan Aruch Yoreh Deah 221:2, Beit Yosef, Taz, Shach Yoreh Deah 222:1
- Shach Yoreh Deah 208:1
- Rama Yoreh Deah 217:48, Shu"t Yabia Omer vol. 8 Yoreh Deah Siman 37:2