Chullin 106a: Not washing before a meal caused a Jew to eat pork. Rashi: There was a Jew who owned a restaurant serving kosher meat to Jews and neveilah meat to gentiles. Once a Jew came and did not wash his hands before eating, so the restaurant owner thought he was a gentile and served him pork.

חולין קו ע”א: מים הראשונים ־ האכילו בשר חזיר. רש”י: שהיה חנוני ישראל מוכר בשר שחוטה לישראל ומבשל ומאכילם וכשהעובד כוכבים בא בחנותו מאכילו נבלות ובא יהודי אחד לאכול ולא נטל ידיו וכסבור זה שעובד כוכבים הוא והאכילו בשר חזיר.

Someone once asked Rav Ovadiah Yosef: “If I can’t find another job, may I work in a treif restaurant, provided that I will not be cooking meat and milk together?”

The question hinges on whether there is any Rabbinic prohibition on working with treife food lest he come to eat it.

Rav Ovadiah quotes the Kesef Mishnah (Tumas Mes 1:2) who says that the reason why it’s forbidden to cook meat and milk together is out of fear that one might come to eat it. This goes into the category of gezeiros made by the Torah itself – similar to yichud. Yet, cooking a non-kosher animal’s meat with milk is allowed (Yoreh Deah 87:3). The prohibition is only on kosher meat (at least a kosher animal) and milk, because people are used to eating it each separately and may accidentally come to eat them together. This shows that there is no prohibition on working with treife food.

The Rashba (3:223) does say that the prohibition on doing business with forbidden food is because one might come to eat it. If so, “doing business” would include even an employee who does not own the business, because he too might come to eat. However, this is only the Rashba, who holds that doing business is a Rabbinic prohibition. According to most Rishonim, it is a D’oraisa, so “one might come to eat it” may not be the reason.

The Gemara in Chullin 106a seems to address this exact question. The Gemara quotes a saying, “Not washing before a meal caused a Jew to eat pork,” and Rashi tells the story of a Jew who owned a restaurant serving kosher meat to Jews and neveilah meat to gentiles. Once a Jew came and did not wash his hands before eating, so he thought the proprietor mistook him for a gentile and served him pork. The Maharsha asks: why did Rashi begin by saying that this Jew served neveilah to gentiles, and then end by saying that he served pork to this customer? He explains that the Jew usually sold neveilah meat – not pork – because one may not deliberately do business with non-kosher, so he sold only the neveilah that resulted from mistakes in shechitah. It was only this time that he happened to have some pork on hand. So we see that the Maharsha was assuming that this proprietor was an observant Jew. If so, we see that it’s okay for a Jew to cook and serve non-kosher food to gentiles.

However, the Beis Yosef (end of 117) argues that the restaurant owner may have been a non-observant Jew, and besides, this story is no proof because, as the Midrash (Bamidbar 20:21) says, the story took place during the period of Greek persecution. The Jew sold pork deliberately in order to hide his Jewish identity, and the hand-washing was a secret cue for the Jews to show him they were Jewish, so that he should serve them kosher meat.

In the end, Rav Ovadiah paskened that this unemployed person should try his hardest to find a different job, in order to follow the stricter opinion. But if there was no other way, he could rely on the Maharsha and take the job in the treif restaurant.  

Chullin 93a: Cheilev that is covered by the meat is permitted. Rashi: Forbidden fat that is on the flanks under the kidneys and visible on the high part of the flanks, and then disappears under the meat, red and spreading under the meat throughout the flanks. As soon as the meat covers it, it is permitted. And when that meat ends below [at the animal’s belly], a thick, white membrane protrudes… under that thick membrane there is cheilev, and some hold that that cheilev is forbidden, because that membrane is not considered “a covering of meat” since it is very thin. But in Germany they permit it. And to me as well, it seems that it is a complete covering.

חולין צג ע”א: אמר רבי אבא אמר רב יהודה אמר שמואל: חלב שהבשר חופה אותו מותר. פירש”י חלב שהבשר חופה אותו ־ חלב שעל הכסלים שתחת הכליות ונראה בגובה הכסלים ואח״כ נבלע תחת הבשר אדום דק ומתפשט תחת אותו בשר בכל הכסלים ומשהבשר חופהו מותר וכשכלה למטה אותו בשר יוצא ממנו קרום עב ולבן, לבד קרום דק וקלוש המתפשט בכל הכסלים שאסור משום חלב כדלקמן, ותחת אותו קרום עב יש חלב ויש שנוהגים איסור באותו חלב לפי שאותו קרום אינו חשוב חפוי בשר שדק הוא אבל בארץ אשכנז נוהגין בו היתר וגם בעיני נראה דחפוי גמור הוא.

Rabbi Yisroel Belsky was once asked to inspect a traditionally reliable kosher restaurant, after someone suggested that they were serving cuts of lamb meat with the cheilev still attached. This establishment would buy the freshest meat and perform their own nikkur, and they employed a mashgiach with many years of experience. “The owner of the restaurant, the butcher, and the mashgiach each inspected the lambs they showed me,” Rav Belsky related, “and were at a loss to explain why anyone would suggest there was any cheilev. Now, all lambs have cheilev attached to the navel, and even though that piece of meat is very tasty, there is no way to clean off the cheilev, and it must simply be cut off and discarded. Unfortunately for this restaurant, they had never identified this piece of cheilev for they mistakenly looked at the meat upside-down, and thought the cheilev was simply a piece of permitted fat. The allegation was indeed true.”

Source: Halachic Responsa From the Desk of Harav Yisroel Belsky, p. 191

Chullin 59a: The characteristics of a kosher grasshopper are that it has four legs, four wings, jumping legs, and its wings cover most of its body. Rav Yehuda said in the name of Rav: This means most of the length of the body. Some say: Most of the circumference. Rav Papa said: Therefore we require them to cover most of the length and most of the circumference.

חולין נט ע”א: ובחגבים: כל שיש לו ארבע רגלים, וארבע כנפים, וקרצולים, וכנפיו חופין את רובו. ובדף סה ע”ב: מאי רובו? אמר רב יהודה אמר רב: רוב ארכו, ואמרי לה: רוב הקיפוֹ אמר רב פפא: הלכך, בעינן רוב ארכו, ובעינן רוב הקיפו.

In approximately 2001, Rabbi Chaim Kanievsky was learning Maseches Chullin and reached the sugyah relating to grasshoppers.  Rav Chaim realized that he needed to see a grasshopper to better understand the Gemara, and asked his daughter to bring him one. She tried, but reported to her father that she failed to find one. He went back to the sugyah, and lo and behold, a grasshopper came hopping through the window, landing on his Gemara. After examining it, he let it go. As he continued through the sugyah, he realized that he needed to study the hind legs a bit more, but the grasshopper was long gone. Before closing his Gemara, a second grasshopper hopped in and on to his Gemara, giving him a chance to study its hind legs in detail.

The story spread quickly. Some time later, a rov giving a shiur in Bnei Brak criticized the tales people tell about gedolim, explaining that the stories cannot all be true, and sound silly. As a case in point, he brought the story of Rav Chaim and the grasshoppers. After the shiur, the maggid shiur went home and found his house infested with grasshoppers. He tried for three days to rid his home of the insects, but could not.  Someone suggested that he go to Rav Chaim and ask for mechilah. The rov approached Rav Chaim and told him what had happened. Rav Chaim laughed, saying that he did not need his mechilah at all, as the grasshoppers could have come to anybody (after all, the window was open!), and he was certainly mochel him if he needed it. The rov went home – and the grasshoppers were gone!

The above story was printed in a certain sefer, about which Rabbi Yaakov Galinsky quipped, “I would say I don’t believe it, but I am afraid a plague of copies of that sefer will occupy my house.”

Source: https://matzav.com/grasshopper-nissim-with-rav-chaim-kanievsky/

Chullin 27b: Animals were created from earth, so they need both the esophagus and windpipe cut. Fish were created from the water, so they don’t require any shechitah. Birds were created from the mud, so they only need one tube cut.

Rema Yoreh Deah 13:1: It is allowed to cut a piece off a live fish and eat it, but it is forbidden to eat a whole fish live because of the prohibition, “Do not make yourself disgusting.”

חולין כז ע”ב: דרש עובר גלילאה: בהמה שנבראת מן היבשה ־ הכשרה בשני סימנים, דגים שנבראו מן המים ־ הכשירן בולא כלום, עוף שנברא מן הרקק ־ הכשרו בסימן אחד.

יורה דעה יג,א בהמה חיה ועוף טעונין שחיטה דגים וחגבים אין טעונין שחיטה: הגה ומותר לאוכלם מתים, או לחתוך מהם אבר ולאכלו, אבל אסור לאכלן חיים משום בל תשקצו.

The Hamodia newspaper recently interviewed Rabbi Boruch Cohn, a rebbi in Lakewood who enjoys fishing in local lakes and streams. Their first question was, “Fishing is not known to be a popular downtime activity in our circles. Is there a good reason for this?”

Rabbi Cohn replied, “I don’t have a clear answer to this one, but it might be that people don’t have the time or perseverance to fish; it’s not a pastime for those who want instant gratification! Another reason could be that they’re prone to associate it with hunting, which is assur. When I was thinking of taking up fishing, I discussed the issue with Dayan Yaakov Posen, shlita, of Washington Heights, where I grew up. He advised me that the issur of tzaar baalei chaim (causing affliction to living things) does not apply to fish and gave me an enthusiastic go-ahead. I have since spoken to several Lakewood poskim on this matter, and they are in full agreement with Dayan Posen.” 

(Hamodia, July 8, 2020, Community p. 25)

[Actually, the problem with hunting, according to the Noda Beyehuda (Tinyana YD 10, brought in Pischei Teshuva YD 28:10), is not tzaar baalei chaim, for two reasons:

1) People use the skins, and there is no prohibition on tzaar baalei chaim when the animal is used for the needs of man. The source for this is Piskei Hatosafos Avodah Zarah 11a, explaining why it is allowed to cut the hooves of the king’s horses after the king dies.  

2) There is no prohibition of tzaar baalei chaim when you are killing the animal, only when you are keeping it alive and suffering. This is based on Chullin 7b, where Rabbi Pinchus ben Yair reprimanded Rebbi for owning dangerous white mules. Rebbi proposed cutting their hooves, but Rabbi Pinchus responded that this would be tzaar baalei chaim. Then Rebbi proposed killing them, to which Rabbi Pinchus responded that it would be bal tashchis – wastefulness. From this exchange we see that killing can never be tzaar baalei chaim.

Rather, the problem with hunting is that killing animals for sport is cruelty. We are enjoined to feel that “His mercies are upon all His creatures” and that is why we don’t say bless someone who buys a new leather garment that he should wear it out and buy a new one (Rema Orach Chaim 223:6). Therefore hunting, unless done for a living, may not be strictly forbidden but it does inculcate a bad midah and is not the right thing for a Jew to do.

Furthermore, going out to the forests where the wild animals live is dangerous, and one is forbidden to place his life in danger. Esav was an expert hunter, yet he testified on himself, “Behold I am going to die,” and the Ramban explains that he was likely to die in his father’s lifetime, so he did not need the birthright. One who hunts to make a living is permitted to risk his life, as it says, “He risks his life for it” (Devarim 24:15). But if he doesn’t need the money, it is forbidden.

According to this, it would seem that fishing for sport should exemplify the same bad midah of cruelty as hunting for sport. Tzaar baalei chaim may not apply, but the midos argument still would.

The Noda Biyehuda’s contention that there is no prohibition of tzaar baalei chaim when killing the animal would seem to be against the Sefer Hachinuch 451, who says that the reason for slaughtering at the neck with a perfectly sharp knife is in order to minimize tzaar baalei chaim. According to the Chinuch, we could prove that the prohibition does not apply to fish from the very fact that no shechitah is required.

The nafka minah between the Noda Biyehuda and the Chinuch would be in the question of whether one may make a fish suffer when not killing it. According to the Noda Biyehuda it is forbidden, while according to the Chinuch it is permitted.

Rabbi Menashe Klein (Mishneh Halachos 6:216) was asked whether someone who has an aquarium in his house is obligated to feed the fish before eating a meal. The questioner had brought proof from the fact that one may cut a piece off a live fish, that there is no prohibition of tzaar baalei chaim on fish. R’ Menashe counters that perhaps there really is tzaar baalei chaim on fish, yet eating from a live fish is allowed because the prohibition on causing pain doesn’t apply when using the animal for human needs. We see, for example, that one may cut off and eat a piece of a ben pekuah (a live baby found inside a slaughtered cow) even though it is alive and certainly feels pain (Taz YD 13:3).  

Then he brings a proof that there is indeed tzaar baalei chaim on fish, from the fact that one may not harness two different kinds of fish to his boat (Bava Kama 55a). The prohibition on harnessing two different species is because of tzaar baalei chaim, since an animal does not like to work together with a different kind of animal (Chinuch 550). If this applies to fish, then clearly there is tzaar baalei chaim on fish. He concludes that one must feed his fish before eating a meal (and therefore recommends not keeping an aquarium, lest one transgress this prohibition when eating away from home).

Thus there appears to be an internal contradiction in the Chinuch. If fish have tzaar baalei chaim, then why is it allowed to eat them without shechitah? And you cannot answer, as R’ Menashe Klein does, that for the purpose of man there is no prohibition, because the Chinuch says that even at the time of shechitah we try to minimize pain.

Rather, the answer is probably that the Chinuch’s approach is merely to suggest reasons for mitzvos (often, as in these two cases, more than one reason for each mitzvah), without being particular that everything he says leads to the same halachic conclusions.]   

Chullin 111a: Perhaps the reason it was allowed to cook the heart and liver was because they dipped them in boiling water, so that the blood was cooked inside the meat and was thus unable to come out. This is similar to the story of Rav Huna, who ate unsalted meat dipped in vinegar, and Rav Nachman, who ate unsalted meat dipped in boiling water.

חולין קיא ע”א אי נמי מיחלט הוה חליט ליה מעיקרא כי הא דרב הונא חלטי ליה בחלא ורב נחמן חלטי ליה ברותחין. וכתב הרי”ף שהגאונים גזרו על זה כיון דאין אנו בקיאין. והערוך השולחן בסימן ס”ט סקס”ח ביאר החשש של הגאונים ואח”כ כתב ומ”מ דעה ראשונה עיקר להלכה ולכן לצורך מותר.

Rabbi Moshe Feinstein was asked by his grandson, Rabbi Mordechai Tendler, how to prepare meat for a person with a heart condition and high blood pressure, whose doctor told him to avoid salt. R’ Moshe said, “There are two ways: the first is to have a separate pot, cut the meat up into small pieces and drop them into vigorously boiling water. Although we don’t usually use this as a method of kashering meat, because the Gaonim say we are not expert in using it, in this case one can be lenient.

“The second way is to use another type of salt, such as ammonium chloride or potassium chloride. The question about this is only whether such salt works to remove blood. If it is a naturally occurring salt, it definitely works. For we see that Sodom salt has different components from our salt, since it causes blindness, yet it works for kashering. But if it does not occur naturally, then we don’t know if it removes blood.”

Rabbi Tendler suggested that the person should do both: first salt with another type of salt, and then drop into boiling water. This way, if the salt doesn’t work, there is at least a chance that the boiling will work. Reb Moshe said perhaps, but one need not do both. He concluded that the first idea would be the best one to use.

Source: Mesores Moshe, v. 1, p. 209

Chullin 111a: Rabbah bar Rav Huna was eating at Rabbah bar Rav Nachman’s house. He noticed that the liver had an artery that was saturated with blood. He said to them, “Why did you do that?” They said: “What should we have done?” He said, “Tear it crisscross and put the torn side down while you roast it.”

קיא ע”א: אשכח ההוא כבדא דהוה בה סמפונא דבליעא דמא, אמר להו אמאי עבדיתו הכי? אמרו ליה: אלא היכי נעביד? אמר להו: קרעו שתי וערב וחיתוכא לתחת.

שו”ע יו”ד ע”ג ס”א: הכבד יש בו ריבוי דם לפיכך לכתחלה אין לו תקנה לבשלו ע״י מליחה אלא קורעו שתי וערב ומניח חיתוכו למטה וצולהו (שיהא ראוי לאכילה) (או״ה נתיב ט״ו) ואחר כך יכול לבשלו… ובדיעבד מותר אם נתתבשל לבדו בקדירה (בלא צלייה) אבל הקדירה אסורה שפולטת ואינה בולעת ויש מי שאוסר. רמ”א: וכן נוהגין לאסור הכל.

A man came to Rabbi Avrohom Pam and said, “My wife bought a whole chicken and didn’t realize that the liver was packed inside. She cooked it in soup, and then served the chicken on china plates. We have no problem throwing out the chicken and kashering the soup pot, but is there any heter to save the china plates?”

Rav Pam replied, “The Shach (73:8) says that although we hold like the opinion that liver needs to be roasted, and therefore if it was cooked one may not eat it, still the plate on which the liver was served after cooking does not become forbidden. The Pri Megadim asks why not – doesn’t pouring from a kli rishon cook the outer layer of the plate? Also, the Shach himself in 74 and 105 holds that a hot piece of solid food (דבר גוש) can transmit taste even when in a kli sheini.

The Chavos Daas answers:

ולענ”ד לא קשיא מידי דהא כתב הש”ך בסימן ק”ה ס”ק י”ח דחתיכה שנאסרה מחמת דם הוי כאיסור בלוע, ושם בס”ק כ”א שאינו מבליע כדי קליפה רק מגוף הדבר אבל מאיסור בלוע אינו בולע אפילו בשמן וכ”ש דם דכחוש הוא ודאי דאינו יוצא מחתיכה בלא רוטב.

“When the solid piece of hot food being placed on the plate is not forbidden on its own, only because of something else that got absorbed in it, then it does not transmit taste to the plate through pouring. And a piece of meat that is forbidden because it contains blood is like any other piece that has something forbidden absorbed in it.”

Therefore, said Rav Pam, the chicken, which contains blood from the liver cooked with it, will not forbid the plate.

[What is puzzling is that although Rav Pam was certainly correct about the chicken, which is only forbidden because it absorbed from the liver, the Chavos Daas says this even regarding the liver itself. He cites as his source the Shach in 105, but the Shach there (105:18) clarifies that he says this only regarding blood absorbed in the meat that came from another source, whereas blood from that piece of meat itself – i.e. if it was not salted properly – would forbid other pieces or plates. Seemingly this liver, which was cooked without roasting, is in that category.

The answer may lie in the second Shach (105:21) quoted by the Chavos Daas. There he says that even though usually fatty tastes absorbed in one dry piece can travel to another dry piece through touch, if the bottom piece (or plate) is cold, it does not travel. If so, possibly even blood that originated within the liver itself cannot travel to the plate under it.

The only problem is that the Chavos Daas says that blood is a כל שכן from fatty tastes, and according to the above explanation it is not really a כל שכן, since here the blood originated in the meat and is therefore worse, in one aspect, than fatty taste that came from elsewhere.]

Source: Rabbi Yisroel Reisman, tape on YD 73:6.

Chullin 110b. Abaye said to Rav Safra, “When you go up to Eretz Yisroel, ask them about liver.” He went up and asked Rabbi Zerika, who replied, “I cooked it for Rabbi Ami and he ate it.” He reported back to Abaye, but Abaye said, “I already knew that liver cooked alone is permitted. What I meant to ask was if it is permitted to cook liver with other meat.”

Tosafos quoting Rabbeinu Tam: This Gemara is talking about unsalted liver, but salted liver is like any other meat that was kashered through salting, and one may cook it with other meat.

חולין קי ע”ב: אמר ליה אביי לרב ספרא: כי סלקת להתם בעי מינייהו, כבדא מה אתון ביה? כי סליק, אשכחיה לרב זריקא, אמר ליה: אנא שלקי ליה לרבי אמי ואכלֹ. כי אתא לגביה, אמר ליה: למיסר נפשה לא קא מיבעיא לי, כי קמבעיא לי ־ למיסר חבירתה.

אומר ר״ת דכולה הך שמעתא איירי בכבד שלא נמלח דאי בתר מליחה ושהייה במלח פשיטא דשרי לבשלה בהדי בשר שעל ידי מליחה יצא כל הדם.

שו”ע יו”ד ע”ג ס”א: הכבד יש בו ריבוי דם לפיכך לכתחלה אין לו תקנה לבשלו ע״י מליחה אלא קורעו שתי וערב ומניח חיתוכו למטה וצולהו (שיהא ראוי לאכילה) (או״ה נתיב ט״ו) ואחר כך יכול לבשלו… ובדיעבד מותר אם נתתבשל לבדו בקדירה (בלא צלייה) אבל הקדירה אסורה שפולטת ואינה בולעת ויש מי שאוסר. רמ”א: וכן נוהגין לאסור הכל.

Rabbi Avrohom Pam and his rebbetzin spent a week in Toronto. When they returned, Rabbi Yisroel Reisman came over to visit, and Rav Pam recounted the halachic questions that had been presented to him over the week.

“A lady bought a whole chicken, with the not-yet-kashered liver in a plastic bag inside the cavity of the chicken. She knew she needed to roast the liver, but since it was frozen, she decided to thaw it out by running hot water on it in the kitchen sink, while still in the plastic bag. Then she realized this might be considered cooking…”

“In whose house did this shailah happen?” the Rebbetzin broke in.

“In the house where we were staying,” said Rav Pam.

“So why didn’t they ask me?!” joked the Rebbetzin.

Rav Pam continued, “I was matir it for a combination of two reasons. First of all, pouring (עירוי) only cooks the outermost layer of an item, and here the outermost layer was the plastic bag, so the liver did not get cooked. This reason alone was not sufficient to permit it, because they ran it under the sink for a long time, and some say that with many pourings, the cooking goes deeper than a layer. The second reason is the opinion of Rabbeinu Tam, brought by the Mechaber in 73:1. The Mechaber that although lechatchilah we follow the opinion of the Rambam and Rif that one must roast the liver, if one followed Rabbeinu Tam and cooked it, even without salting, it is kosher. The Rema says that we are strict even after the fact. But in this case, where we have the first reason too, I was matir it.” 

“If they had asked me, I would have said that too!” exclaimed the Rebbetzin.

Source: Rabbi Yisroel Reisman, tape on YD 73:3-6.

Chullin 95a: If there are nine stores that sell kosher meat and one that sells non-kosher meat, and a person bought from one of them but does not know which one, it is forbidden.

תא שמע: תשע חנויות כולן מוכרות בשר שחוטה, ואחת מוכרת בשר נבלה, ולקח מאחת מהן, ואינו יודע מאיזה מהן לקח ־ ספקו אסור.

יו”ד סימן ק”י סעיף ה: מי שלקח בשר מהמקולין ואפילו חתיכה הראויה להתכבד ונמצאת טרפה במקולין ולא נודעו חתיכות הטרפה ואינו יודע מאיזו לקח, כל מה שלקחו מהמקולין קודם שנמצאת הטרפה מותר שלא נפל הספק בקבוע אלא לאחר שפירש וכיון שהרוב כשר מותר, אבל ליקח מכאן ואילך אסור ואפילו חתיכה שאינה ראויה להתכבד שאין הכל בקיאין בזה ויטעו בין ראויה להתכבד לשאינה ראויה.

Shortly before Pesach 2013, the owner of Doheny Glatt Kosher Meats in Los Angeles was caught on camera instructing his employees to bring boxes of unsupervised meat into his store. The video, shot by a private investigator, showed the owner waiting until the mashgiach left the premises and then having the boxes carried in from the back of his SUV.

On Sunday, the 13th of Nisan (March 24, 2013), staff members from the Rabbinical Council of California (RCC) as well as a handful of other rabbis and lay leaders from the Orthodox community gathered to watch the incriminating video in the office of Rabbi Kalman Topp, rav of Beth Jacob, the largest Orthodox synagogue in Pico-Robertson. Also present were Rabbi Elazar Muskin of Young Israel of Century City and Rabbi Yosef Kanefsky of B’nai David-Judea. After watching, the rabbis called in the store owner, who admitted that he brought in the unsupervised meat, although he claimed it was kosher.

Based on this information, the RCC revoked its certification from Doheny effective on March 24 at 3 PM. They stated, however, that any meat bought from the store before 3 PM on that day was considered kosher. Rabbi Yisroel Belsky was consulted and he also agreed with this ruling.

The reason is based on the rule that when it comes to kavua d’rabanan, there is no kavua lemafrea.

To explain: our Gemara is talking about a case when the non-kosher store was recognizable as such all along. This is kavua d’oraisa. If later on it became recognizable as treif, but it was not recognizable at the time of purchase, there is a dispute between the Ran and the Rashba as to whether the stringency of kavua applies retroactively. We pasken like the Rashba that it does apply. So, for example, let’s say the investigation had revealed that ALL the meat at Doheny was treif. A sign was promptly hung in the store window at 3:00 PM saying that the hashgacha was removed. Then someone came to a rav and asked, “I bought this meat at 2:00 PM and I’m not sure if I bought it from Doheny or one of the other 9 stores in Los Angeles.” The rav would tell him it is forbidden because it is kavua lemafrea.

However, in our case not all the meat in the store was treif. It was only 8 boxes of questionable meat out of about 300 coming into the store that day. There is no kavua d’oraisa, even retroactively, because it was never recognizable, even later, which pieces of meat were treif. But what about kavua d’rabanan? The Rabbinic rule that “a piece fit to serve to an honored guest” does not become nullified in a mixture is called kavua d’rabanan (see Zevachim 73a and 73b, and Tosafos on 73b s.v. ela), because it follows similar rules to those of kavua d’oraisa: you are not allowed to take directly from the mixture, but if somehow a piece got separated from the mixture on its own, you are allowed to eat it. Does this rule also operate retroactively? The Shulchan Aruch (110:5) rules that it does not. Thus  if Doheny was selling hundreds of nice pieces of meat fit for a guest, and it was discovered at 3:00 that a small fraction of them were treif, those pieces purchased before the discovery are not forbidden. After the discovery, all the meat in the store is forbidden, even the ground and chopped meat, because people might confuse it with the big pieces fit for a guest. )