The Odd Account of the Overnight Onion
Those of us fortunate to be learning Daf Yomi are approaching the final countdown to the worldwide grand Siyum HaShas, celebrating seven-and-a-half years of daily determination, persistence, and unyielding commitment to Torah that is required to complete all of the Talmud Bavli. There are celebrations planned for well over 150,000 people (!) in many places throughout the globe, including the former Yeshivas Chachmei Lublin in Poland (birthplace of the Daf Yomi), Binyanei Ha’uma in Jerusalem (of course), a massive temporary structure outside Ashdod currently being built expressly for this event, and the single largest venue - the gargantuan MetLife Stadium (a.k.a. Giants’ Stadium) in New Jersey (yes, contrary to reason and popular belief, the New York football teams actually play in New Jersey). This certainly exemplifies the dictum recited at a Siyum, “Anu Ratzim, V’Heim Ratzim…”
Recently, Daf Yomi learners worldwide came upon a fascinating Gemara in Maseches Nida, the last Tractate in the Talmud. The Gemara cites an extremely strong yet puzzling statement by Rabbi Shimon Bar Yochai. He states that one who eats a peeled onion, egg or garlic that has been left sitting out overnight is literally endangering his life, and will be ultimately judged as a person who took his own life! The cause of this prohibition is a “Ruach Ra’ah,” a type of spirit of impurity or spiritual contamination that rests upon these three foods when peeled and left overnight.
The reason why this statement is considered intriguing is that although there does not seem to be a dissenting opinion in the Gemara, considering the severity of both the offense and the punishment stated, nevertheless, this prohibition is not codified by the classic halachic codifiers. Astoundingly, there is absolutely no mention of this proscription in any of the works of the greatest Jewish doctor, the Rambam, and nothing in the Rif, Tur, or Shulchan Aruch!
Yet, many later authorities, including the Pri Chodosh, Shulchan Aruch Harav, Chida, Ben Ish Chai, and Aruch Hashulchan, do cite the Gemara’s statement, and consequently rule that eating a peeled egg, onion or garlic that sat overnight is strictly forbidden. So how is it that it is not mentioned at all by the great halachic codifiers?
This question has baffled many for years and there is no clear-cut, one-size-fits-all solution. There are, however, several different perspectives that the halachic authorities take on this matter.
No More Ruach Ra’ah?
One way of understanding the codifiers’ deafening silence on this issue is that they may have been of the opinion that Ruach Ra’ah is no longer applicable. This is not a new argument, but rather one that many Rishonim cite, including the Maharam M’Rottenberg, the Mordechai and Tosafos.  Additionally, as is well-known, the Rambam himself did not hold of any sort of Ruach Ra'ah. The Rashal as well famously declared that Ruach Ra’ah is no longer prevalent among us. Several later authorities rule this way, maintaining that peeled overnight onions no longer give us any reason to worry about and may be eaten. They maintain that this is the reason there is nary a mention of it by the great codifiers, and not due to any lacunae in their knowledge.
Ruach Ra’ah Still Abounds
Yet, as mentioned previously, many later authorities maintain that this prohibition still applies in full force, as once an issue is mentioned in the Gemara as a halachic problem, it cannot be discounted simply because many codifiers did not quote it. Also, several authorities suggest that the Maharam did not actually discount Ruach Ra’ah completely. On the contrary, they assert, he only entertained that leniency as a possible solution and not necessarily as a definitive ruling. Additionally, it can be argued that Tosafos and the Rashal were referring exclusively to a specific type of Ruach Ra’ah that no longer is applicable; the Ruach Ra’ah associated with overnight peeled eggs and onions may therefore still be pertinent. These Poskim therefore maintain that it is strictly prohibited to eat a peeled onion, egg, or garlic that was left out overnight. 
The Middle Road
A third approach to this issue is to synthesize the other approaches, taking all of the above into account. These authorities, including the Chofetz Chaim, Rav Moshe Feinstein, and the Steipler Gaon, maintain that if one wishes to be lenient, one definitely has what to rely upon. Yet, they recommend following the strict approach: not to partake of peeled overnight eggs, onions, and garlic.
Even if one wishes to follow the recommended route of not eating overnight peeled onions, there are several important exclusions to the rule:
- The Gemara itself cites an exception: If some (even a tiny amount) of the original outer layer, peel, shell, or root hairs remain, then one need not worry about Ruach Ra’ah, as it is not considered to be peeled.
- Many Poskim rule that if the overnight onion was mixed together with another food item, such as part of a salad, then it would be permitted, as it lost its status of purely being an onion or an egg. Several contemporary authorities, including the Ben Ish Chai, Chazon Ish, Rav Shlomo Zalman Auerbach, and the Minchas Yitzchak, maintain that this holds true even if only a small amount of salt, sugar, flour, or oil was added to the onion or egg, that it no longer is considered a mere peeled egg or onion, but rather as part of a mixture, which Ruach Ra’ah cannot affect.
- Some suggest a quite questionable leniency that if one wraps the peeled egg or garlic up well and then puts it in the fridge, it would consequentially be considered protected from Ruach Ra’ah. The reason why many question, and ultimately reject, this supposition is that the Gemara explicitly states that even if the peeled onion is covered and wrapped up, it is still susceptible to Ruach Ra’ah. Therefore, most authorities do not abide by this leniency at all. Yet, others differentiate between how it was closed, for if it was hermetically sealed (which wasn’t around at the time of the Gemara), some opine that it is as if it is still in its shell, and rule that it is permitted.
- Another opinion cited by many authorities is that Ruach Ra’ah does not affect dried onion powder, garlic powder, or powdered eggs, as not only are they not considered the original food item, but they are not even considered a food at all, rather a powder.
Commercial Uses and Bakeries
A common question debated among contemporary authorities is what bakeries should do. Are they required to throw out trays of unused leftover eggs, and not use them the next day?
Several authorities, including the Yad Meir and the Rav Shmuel Halevi Wosner, rule that nowadays the Ruach Ra’ah is non-applicable and therefore bakeries need not worry about this problem at all. Others, including the Minchas Yitzchak, Tzitz Eliezer, and Rav Ovadiah Yosef, maintain that although personally one should be stringent, nevertheless, in a commercial setting since there are many mitigating factors and rationales present (as sugar and/or salt often get added to the mix; in addition, the prohibited amount might have actually been nullified, etc.), it is permitted.
Rav Moshe Feinstein rules leniently as well, but from a different perspective. He posits that there is no Ruach Ra’ah when a company cracks eggs or peels garlic that will not be used for many weeks or months. He explains that Ruach Ra’ah only applies when someone is preparing food for the next day, as that would have been the standard scenario the Gemara was referring to, not for weeks later. Accordingly, bakeries would be included in this exception.
Still, there are several contemporary authorities, chief among them the Klausenberger Rebbe, who did not allow any dispensation for industrially produced items, and exhorted extreme caution with all facets of this halacha, ruling that peeled overnight eggs, onions, or garlic are strictly prohibited in all cases (unless part of a mixture). He even once publicly asserted that negligence and lackadaisicalness with eating overnight peeled eggs and onions might be the cause for cancer, Rachmana litzlan! This is why although many Poskim allow leniency when it comes to bakeries (due to the aforementioned rationales), nevertheless, bakeries run by Sanz and Klausenberg Chassidim are very stringent with this.
To sum up the matter, whether or not Ruach Ra’ah still exists today, it would seem that generally with a little bit of effort, we can minimize the possibility of it affecting our food. So, when next preparing an egg salad or garlic spread, it seems quite worthwhile whenever possible to strive to follow the guidelines that ensure “spiritual contamination” remains far from our food.
Postscript: Davar Charif
There is an additional aspect of halacha that onions and garlic (and other sharp foods including horseradish, radishes, and certain types of peppers, etc., but not eggs) strongly impact: that of “davar charif.” This term refers to a food item that imparts extremely sharp taste, and it causes some of the most common and complicated kashrus questions. This is because in some ways, when added to an equation, a davar charif can be a “game-changer.” Due to its strong taam, under certain conditions a davar charif has the unique ability to negate a hetter of Nat Bar Nat, and “re-awaken” absorbed taste long considered inert and irrelevant. Moreover, when cooked in a dairy or meat pot, or sliced with a dairy or meat knife, even without meat or milk being present, a davar charif can revert the imparted taam, and in some ways make it as as if one was actually cooking with or cutting meat or milk. Many of the exact nuances of its status and application thereof are debated among authorities, and the Tur, Shulchan Aruch, andRema and their main commentaries dedicate more than an entire Siman to davar charif’s minutiae. In other words, we should all be aware that halachically speaking, the onion gives quite a sharp “kick.”
This article was written L'iluy Nishmas Shoshana Leah bas Yaakov Eliezer, Yisrael Eliezer bas Zev, and the Rosh HaYeshiva - Rav Chonoh Menachem Mendel ben R' Yechezkel Shraga and l’zechus for Shira Yaffa bas Rochel Miriam v’chol yotzei chalatzeha for a yeshua sheleimah teikif umiyad!
For any questions, comments or for the full Mareh Mekomos / sources, please email the author: firstname.lastname@example.org.
Rabbi Yehuda Spitz, author of M’Shulchan Yehuda on Inyanei Halacha, serves as the Sho’el U’Meishiv and Rosh Chabura of the Ohr Lagolah Halacha Kollel at Yeshivas Ohr Somayach in Yerushalayim. He also currently writes a contemporary halacha column for the Ohr Somayach website titled “Insights Into Halacha”. http://ohr.edu/this_week/insights_into_halacha/.
 Perhaps this may also be a fulfillment of the Gemara’s explanation of Zecharia’s nevuah (Ch. 9:7; Megillah 6a) that the theaters and circuses of Edom will in the future be used for “Sarei Yehuda lelamed bahen Torah B’Rabbim.”
 Nida (17a). Also stated in Derech Eretz Rabba (Ch. 11).
 Rashi (ad loc. s.v. umischayav), as explained by the Aruch LaNer (ad loc.). See also the Maharsha’s explanation (ad loc.).
 Although, as Rav Tzadok Hakohen M’Lublin (Tiferes Tzvi on Y.D. 116) points out in a related topic, the Rambam’s omission of this halacha may not be a strong proof, as the Rambam himself did not hold of any sort of “Ruach Ra’ah,” as proven in his Shu”t Pe’er Hador (146) and cited by the MaharamElshakar (Shu”t 79) and Kessef Mishneh (Hilchos Issurei Biyah Ch. 21:1). See also Shu”t Mishnah Halachos (vol. 6:61) and the Forward (Ch. 7 and 8) to Mv”R Rav Yosef Yitzchak Lerner’s excellent Shemiras Haguf V’Hanefesh. As it is well known that the Rambam seems not to have been concerned with this issue, Rav Tzadok Hakohen asserts that practically, although we cannot simply rely on the Rambam’s expertise as a doctor to avoid this spiritual danger, and we therefore must still remain vigilant with Spiritual dangers. Yet, he nonetheless concludes, citing “Morei HaHora’ah,” that ‘b’makom Mitzva ul’tzorech Shabbos V’Yom Tov’ we can be meikil, as it is stated in Koheles (Ch. 8:5): “Shomer Mitzva lo yeida davar ra.” [See Rema (O.C. 455) for a precedent for this.] The Yaskil Avdi (Shu”t vol. 8 Y.D. 14:4,2) rules this way lemaaseh, that certainly eggs or onions left overnight that were intended for Seudas Shabbos, may still be used due to this dictum.
 Pri Chodosh (Y.D. 116:9), Knesses Hagedolah (ad loc. Hagahos on Beis Yosef 27 and on), Shulchan Aruch Harav (C.M. Shemiras Guf V’Nefesh, 7), Menoras Hama’or (Ner 6), Chida (Birkei Yosef, Y.D. 116:10), Zivchei Tzedek (ad loc. 61), Ben Ish Chai (Year 2, Parashas Pinchas 14), Aruch Hashulchan (Y.D. 116:22), and Kaf Hachaim (ad loc. 92). However, there are other later authorities, including thePischei Teshuva,Chochmas Adam,andKitzur Shulchan Aruch,whose exclusion of this issue remains quite conspicuous.
 Maharam M’Rottenberg, cited by the Mordechai (Shabbos, Ch. 7, Chiddushei Anshei Sheim 3; Hagahos Mordechai Ch. 8 s.v. u’mibeitza), Tosafos (Yoma 77b s.v. mishum; Chullin 107b s.v. hasam), Rashal (Yam Shel Shlomo, Chullin Ch. 8:12). However, it should be noted that the prohibition is mentioned by several other Rishonim, including Tosafos (Shabbos 141a s.v. hani and Beitza 14a s.v. ika), the Rosh (Beitza 14a:21), the SMa”K (Mitzva 171), and Terumas Hadeshen (cited in Leket Yosher, Y.D. pg. 6; see also Terumas Hadeshen 211, where he writes that we should still be choshesh for the sakanos mentioned by Chazal).
 Including the Aderes (Kuntress Over Orach, 4), Shu”t Pri Hasadeh (vol. 3:61 and 62), Shu”t Yad Meir (19; cited in Darchei Teshuva 116:74, “shelo b’chinam hishmitu HaTur V’HaMechaber v’chol HaPoskim din zeh, ki mei’HaYerushalmi mashma d’ain b’zeh issur m’tzad Ruach Ra’ah b’zman hazeh’ al kein yafeh minhagan shel Yisrael she’ain nizharim, lo b’shum kaluf, v’lo b’beitzah klufa”), Shu”t Kav Zahav (14), and Mishmeres Shalom (Y.D. 116:4). The Har Tzvi (Shu”t vol. 2, Y.D. 74 s.v. od) also seems to accept this. The Rema (O.C. 328:35) citing the Shibolei Leket (123), implies as well that Ruach Ra’ah is no longer a sakana.
 Including those authorities mentioned previously, as well as Shu”t Beis Shlomo (vol. 1, Y.D. 189), the Maharsham (Shu”t vol. 4:148 and Daas Torah, O. C. 513:6), Shlah (Shaar Ha’Osiyios pg. 129), Reishis Chochma (Ch. Derech Eretz, Shaar 3, s.v. v’garsinan), Yeish Nochlin (15), Shevet Mussar (end Ch. 40), and Shu”t Shem Aryeh (from the Arugas Habosem;Y.D. end 56). The Maharsham proves from the fact that the Maharam prefaced his leniency with “dilma,”that it shows that he did not truly mean to rule leniently. However, the Sdei Chemed (Maareches HaLamed 141:31 s.v. ha’oleh and Klalei HaPoskim beg. 16; cited in Shu”t Yabia Omer vol. 2, Y.D. 7) maintains that the Maharam used “dilma” as a “lashon anavah,” but definitely did intend to rule leniently. The argument that Tosafos and Rashal were only lenient with a specific type of Ruach Ra’ah is made by the Divrei Yatziv (Shu”t Y.D. vol. 1:31, 4), Chelkas Yaakov (Shu”t vol. 3, Y.D. 39:3), and Ba’er Moshe (Shu”t vol. 3:115, 2, in the brackets).
 Interestingly, overnight peeled eggs might actually be permitted according to several authorities, as Rashi (ad loc. s.v. she’avar) when explaining the prohibition, omits eggs from the criteria. [See also Tashbetz (Chiddushei Rashbatz ad loc.), Rashash (ad loc.), Ben Yehoyada (ad loc.), Ben Ish Chai (ibid.), Shu”t Igros Moshe (Y.D. vol. 3:20 s.v. v’gam ayin Rashi), and Shu”t Yaskil Avdi (vol. 7, O.C. 44:4) on this topic.] Additionally, there is some debate among several later Poskim about what type of peeled eggs are intended for inclusion in the prohibition, cooked eggs or raw eggs. See Shemiras Haguf V’Hanefesh (vol. 1, Ch. 3:2 and 4, and relevant footnotes for explanation)at length. Nevertheless, the common custom is that both raw and hardboiled peeled eggs are considered to be affected by Ruach Ra’ah. See Shu”t Minchas Yitzchak (vol. 4:108, 2) and Shu”t Shulchan Halevi (Ch. 23:3). Yet, as the Tzitz Eliezer (Shu”t vol. 18:46) notes, there will always be a sfek sfeika to permit it b’dieved, as whichever type of egg one peels that was left overnight, raw or cooked, it is always possible that Ruach Ra’ah is actually exclusive to the other type. That, coupled with the Maharam’s shittah, plus the opinions who say eggs are excluded, should allow room for leniency, especially l’kavod Shabbos, as per the psak of Rav Tzadok HakohenM’Lublin and the “Morei HaHora’ah.”
 Including the Chofetz Chaim (Likutei Halachos, Nida 17a, Ein Mishpat 7), Rav Yosef Chaim Sonnenfeld (Shu”t Salmas Chaim, old print vol. 4:4, 8), Rav Moshe Feinstein (Shu”t Igros Moshe, Y.D. vol. 3:20), the Steipler Gaon (cited in Shemiras Haguf V’Hanefesh vol. 1: Ch. 3, end footnote 1), the Debreciner Rav (Shu”t Ba’er Moshe vol. 3:115, 2), Rav Shlomo Zalman Auerbach (Halichos Shlomo on Tefilla Ch. 2, footnote 103), the Minchas Yitzchak (Shu”t vol. 2:68, 13), Rav Yisrael Yaakov Fischer (Shu”t Even Yisrael vol. 9:126, 3), the Tzitz Eliezer (Shu”t vol. 18:46), the Az Nidberu (Shu”t vol. 11:47), Rav Moshe Sternbuch (Shu”t Teshuvos V’Hanhagos vol. 3:256 s.v. uv’ir hakodesh), Rav Ovadiah Yosef (Shu”t Yabia Omer vol. 2, Y.D. 7), the Shevet Hakehasi (Shu”t vol. 2:247), and Rav Yisroel Belsky (Shu”t Shulchan Halevi Ch. 23:3). Mv”R Rav Yaakov Blau zt”l of the Badatz Eidah Hachareidis told this author that one should certainly be choshesh for Ruach Ra’ah, as in his opinion, we cannot simply discount an issue that is explicitly mentioned in the Gemara.
 Including the SMa”K (ibid.), Zivchei Tzedek (ibid.), Ben Ish Chai (ibid.), Chazon Ish (cited in Shemiras Haguf V’Hanefesh ibid. pg. 25, footnote and Orchos Rabbeinu vol. 1, top of pg. 210), Tosefes Chaim (cited in Sefer Mataamim, Erech Yayin Seuda, 18), Kaf Hachaim (ibid.), Halichos Shlomo (ibid.), Shu”t Tzitz Eliezer (ibid.), Shu”t Yaskil Avdi (ibid.; regarding a fried egg – as it was fried in oil), Shu”t Yabia Omer (ibid. 4 and vol. 10, Y.D. 9; adding that this certainly holds true regarding mayonnaise), Shu”t Divrei Shalom (vol. 6:pg. 293, Piskei Teshuvos 199), and Taamei HaMinhagim (Likutim 16). Rav Yisroel Belsky (Shu”t Shulchan Halevi ibid.) is lenient if the chemical balance (pH) is changed even slightly by adding the salt or sugar. The Minchas Yitzchak (Shu”t vol. 6:75) only allows salt and sugar if it is at least two percent of the mixture. [See Shemiras Haguf V’Hanefesh (vol. 2, Miluim, top of pg. 802 for an explanation from Mv”R Rav Yaakov Blau of the Eidah Hacharedis]. Rav Moshe Sternbuch (Shu”t Teshuvos V’Hanhagos ibid.) is lenient lechatchilla only if the color is changed by the mixture. The Klausenberger Rebbe (Shu”t Divrei Yatziv ibid. 14 s.v. u’lemaaseh and Y.D. vol. 1:32, 3) maintains that one may only rely on this if the taste is actually changed by adding the salt or sugar; he further rules that one may not use eggs, garlic or onions as the other ingredient in the mixture.
 Shu”t Rivevos Efraim (vol. 3:495 and vol. 5:523) and Shu”t Vayaan Dovid (Y.D. 119). The Tzitz Eliezer (ibid.) rules that one may rely on this in cases of great loss, as there are many sniffim lehakel. The Chazon Ish (cited in Orchos Rabbeinu vol. 1, pg. 210:16) ruled similarly regarding a raw egg that was left out, that covering it was sufficient. [It is unclear, however, if he held that the same would apply to onions and garlic as well, as it is possible he was referring to the egg exclusion; additionally, perhaps he held that Ruach Ra’ah only affects cooked eggs.]Conversely, in Shu”t Rivevos Efraim (vol. 4:51 s.v. b’siman) a dissenting opinion is presented, that the Gemara (as well as the later authorities who rule this way, e.g., Shulchan Aruch Harav ibid. et al) explicitly rules that this leniency is not valid. Rav Ovadiah Yosef (Shu”t Yabia Omer vol. 10, Y.D. 9) rules similarly, based on a precedent of the Ben Ish Chai’s (Shu”t Rav Pe’alim vol. 2, Y.D. 13). The same point is strongly made in Shemiras Haguf V’Hanefesh (vol. 1, pg. 23: footnote 5, s.v. v’davar).
 Shu”t Shulchan Halevi (ibid.).
 Including Shu”t Degel Efraim (28), Darchei Teshuva (ibid.; who cites the Degel Efraim with no dissenting opinion), Shu”t Har Tzvi (ibid.; albeit due to relying on the Maharam - see Shemiras Haguf V’Hanefesh vol. 1, pg. 28, end footnote 12), Shu”t Chelkas Yaakov (ibid.), Shu”t Ba’er Moshe (ibid.), Shu”t Shevet Halevi (ibid.), Shu”t Yabia Omer (ibid.), and Shu”t Shulchan Halevi (ibid.). Commercially sold onion and garlic powder would also be included in Rav Moshe’s hetter mentioned later in this chapter. See also Shulchan Aruch (O.C.202:16), that there is no bracha recited on dried-out “Tavlin” used to spice-up other foods, as at that point it is no longer halachically considered a “food” that is normally eaten by itself.
 Shu”t Yad Meir (19; cited in Darchei Teshuva 116:74), Shu”t Shevet Halevi (vol. 3:169 and vol. 6:11:5, 7, and 9), Shu”t Yaskil Avdi (vol. 7, O.C. 44:4). The Har Tzvi (Shu”t vol. 2,Y.D. 74 s.v. od) seems to accept this as well.
 Shu”t Minchas Yitzchak (ibid.; however see Shu”t Teshuvos V’Hanhagos ibid. and Shemiras Haguf V’Hanefesh vol. 2, Miluim, top of pg. 802 for an explanation from Mv”R Rav Yaakov Blau of the Eidah Hacharedis), Shu”t Tzitz Eliezer (ibid), Shu”t Yabia Omer (ibid.; although he is hesitant to rely on this alone, he prefers that sugar be added with the eggs, as anyway they are usually meant for cakes; see also Yalkut Yosef,Kitzur Shulchan Aruch Y.D. 113:18), and Shu”t Az Nidberu (ibid.).
 Shu”t Igros Moshe (Y.D. vol. 3:20). See also Mesores Moshe (vol. 1, pg. 238:66). Although Rav Menashe Klein (Shu”t Mishnah Halachos vol. 12:21 s.v. u’mah) argues on this, maintaining that there should be no difference whether the onions and eggs are peeled many weeks in advance or the previous night, nevertheless, it is worthwhile to read Rav Yisroel Belsky’s strongly worded defense of Rav Moshe’s shittah. He writes (Shu”t Shulchan Halevi ibid. s.v. u’lemaaseh) that since the issue at hand is one of spiritual danger, once the universally recognized Gadol Hador rules that it does not apply, it is certain that no spiritual contamination will affect someone who relies on his ruling; see GemaraPesachim (112b) that mazikim are subservient to the wishes of the Gedolim.
 Shu”t Divrei Yatziv (Y.D. vol. 1:31; the quote about causes of cancer is found in a footnote in the responsum) at length. See also Tuvcha Yabiu (vol. 2, pg. 316) from Rav Yitzchak Zilberstein. Other contemporary Poskim who rule stringently include the Chelkas Yaakov (Shu”t vol. 3-Y.D. 39) and Mishnah Halachos (Shu”t vol. 12:20 and 21), following the ruling of the Maharsham and Beis Shlomo (ibid.) et al. Rav Moshe Yehuda Leib Landau of Bnei Brak was also known to be very makpid with bakeries under his hashgacha regarding this halacha.
 Nat Bar Nat and its application is discussed at length in a previous article titled “The Great Dishwasher Debate.” Davar charif’s ability to “re-awaken” imparted taste long considered “dead” denotes that it can cancel out a hetter of aino ben yomo. Meaning, in many instances, if the pot or cooking utensil in question has not been used with actual hot milchigs or fleishig for the last twenty-four hours, it can only impart a weak, pagum taste and usually can no longer affect a sheilah. Yet, when introducing a davar charif into the mix, it can “re-awaken” that taste, and the hetter of aino ben yomo may no longer be applicable to the case in question. See next footnote. Davar charif questions are among the most complicated kashrus questions a halachic authority is generally asked and every Rav “worth his salt” must be well versed in its intricacies.
 The inyan of Davar Charif’s exceptional abilities is based on the Gemara’s assessment in Avodah Zarah (39a) regarding “kort shel chiltis,” that “af al gav d’amar Mar nosein taam l’fgam muttar, agav churfeih d’chiltisa mei’chalia leih shamnunisa, v’haveih leih k’nosein taam l’shvach, v’assur.”
 Yoreh Deah 96 and other se’ifim scattered throughout Hilchos Issur V’Hetter, including 95:2, 103:6, 108:1, 121:7, and 122:3. There is even a recent sefer entirely dedicated to this topic, aptly titled “Davar Charif.”
Disclaimer: This is not a comprehensive guide, rather a brief summary to raise awareness of the issues. In any real case one should ask a competent Halachic authority.
L'iluy Nishmas the Rosh HaYeshiva - Rav Chonoh Menachem Mendel ben R' Yechezkel Shraga, Rav Yaakov Yeshaya ben R' Boruch Yehuda, and l'zchus for Shira Yaffa bas Rochel Miriam and her children for a yeshua teikef u'miyad!