MEAT THAT WAS NOT WATCHED [Kashrus: Basar she'Nis'alem Min ha'Ayin]
Gemara
(Rav): Meat that was not (constantly) watched is forbidden.
Question (Beraisa - Rebbi): When the butchers in the meat markets are Yisraelim, meat found in a Nochri's hand is assumed to be Kosher.
Answer: Meat found in a Nochri's hand is different.
Question (Beraisa): If nine stores in the city sell slaughtered meat and one sells Neveilah, if meat is found, we follow the majority.
Answer: It was found in a Nochri's hand.
Question (Mishnah): If pieces of meat were found outside Yerushalayim, they are permitted.
Answer: Rav explains that this does not permit eating them;
(Rav): The pieces are not Tamei like Neveilah (but one may not eat them);
(Levi): One may eat them.
Rav's did not explicitly say his law. It was inferred. Once Rav saw a man washing a head in the river. It fell in. The man took a basket and scooped out two heads. Rav forbade both, for the new head was probably forbidden.
Question: What difference does it make whether or not Rav explicitly said his law?
Answer: Perhaps Rav said so only in a city where most butchers are Nochrim.
Support: Rav said that forbidden meat is more common.
Question: According to Rav, how is one allowed to eat meat?
Answer #1: It was watched from Shechitah until it was eaten.
Answer #2: It is wrapped and sealed, or there is a special Siman on it.
Rav visited his son-in-law. He looked through a crack in the door and saw hanging meat. He knocked, and everyone came. Only Rav kept watching the meat.
Rav: (If not for me,) would you feed my grandchildren Isur?!
On Erev Yom Kipur, ravens dropped livers and kidneys.
Rav Nachman: They are permitted. Most meat slaughtered today is Kosher.
Bava Metzi'a 24a: A vulture took meat from the market and deposited it among Bar Meryon's trees. Abaye permitted it to him.
Question: Rav said that meat that was not watched is forbidden!
Answer: The case is, he was watching from when the meat was taken.
R. Chanina found a slaughtered kid. Rabanan ruled that we assume that the Shechitah was Kosher.
Rava: The city was mostly Nochrim. It was permitted because most of the Shochtim were Yisrael.
Rishonim
Rif (33b): The Halachah follows Rav.
Ran (DH Karkesha): The Rif and Rambam rule like Rav, even though Levi argues with him. The episodes in the Gemara show this. Even though we asked 'according to Rav, how may one eat meat?', this does not mean that the Halachah does not follow him. Rather, according to Rav, how may we eat meat? The Gemara (44a) says similarly 'according to Rav Papa, our Mishnah is difficult', even though the Halachah follows him. Rashi and the Ba'al ha'Ma'or rule like Levi. Bava Metzi'a 24a supports this. R. Chanina found a slaughtered kid. It was permitted because most of the Shochtim were Yisrael. According to Rav we should be concerned for ravens! They asked about Abaye's ruling to see whether he must hold like Rav, or if we can answer that he need not hold like Rav. Alternatively, we asked also according to Levi. Levi permits only when we did not see ravens. Also he is concerned when we saw a bird deposit meat, lest it brought it from the majority of the world.
Question: The episode on Erev Yom Kipur is surely like Levi, and we are not concerned for the majority of the world!
Answer (Ran): We can say that they saw the ravens take the meat from the city.
Rambam (Hilchos Ma'achalos Asuros 8:11): If meat was found in the market, if most of the sellers are Nochrim, it is forbidden. If most of the sellers are Yisre'elim, it is permitted.
Rambam (12): Similarly, if meat was found in a Nochri's hand and we do not know from whom he bought, if the sellers were Yisre'elim, it is permitted. This is Torah law. Chachamim forbade all meat that is found, whether in the market or in a Nochri's hand, even though all the sellers and all the Shochtim are Yisre'elim. Further, even one who bought meat and put it in his house and it was not watched, it is forbidden, unless he had a Siman in it or recognizes that this is surely it, or it was wrapped and sealed.
Hagahos Maimoniyos (6): Also Rav Hai Gaon, R. Chananel and the Rif rule like Rav. All Chachamim of France rule unlike Rav, for many Mishnayos oppose him.
Rosh (7:20): Rav forbids even in a city where most of the Shochtim are Yisrael. We are concerned lest ravens switched it with a Neveilah. It is clear from our Sugya that we are concerned even for a whole animal. This is an excessive stringency.
Shach (YD 63:6): The Rosh learns from the case in which Rav visited his son-in-law. However, Tosfos (95b DH Lo) says that we cannot learn from here that Rav forbids unwatched meat, for perhaps most of the Shochtim in the city were Nochrim (and surely, all forbid then). If so, there is no source to be concerned for Sheratzim regarding a whole animal. We are not concerned lest Sheratzim took and returned meat on a nail (Sa'if 2), so all the more so we are not concerned for a whole animal!
Rebuttal (Dagul me'Revavah): Tosfos holds that the stringency applies even to a whole animal. He merely says that we cannot prove Rav's opinion from the episode, for perhaps most of the Shochtim were Nochrim.
Rosh (22): We hold like Rav. Rashi says that the Halachah does not follow Rav. He brings a proof from the episode on Erev Yom Kipur in which Rav Kahana permitted livers and kidneys that ravens dropped on Erev Yom Kipur. Also, the Stam Mishnah permits found meat. The Gemara gives weak answers. The Gemara asked 'according to Rav, how is one allowed to eat meat?' It did not ask 'how may we eat meat?' This is like above (11a), that we asked 'how can R. Meir (who is concerned for the minority) eat meat?'; the Halachah does not follow him. This is difficult, for in Bava Metzi'a, Abaye was Machshir meat that a vulture dropped. The Gemara asked from Rav's teaching. This shows that the Halachah follows Rav. R. Tam's text (and the Yerushalmi - Tosfos Bava Metzi'a 24b DH Asa) says that Rav was Machshir it. We challenged Rav from his own teaching. The Rashbam answered that here we rule unlike Rav when the meat was found in the same place it was left. We can say that these episodes were in cities that are mostly Nochrim, so there is more concern (that it was switched with Neveilah).
Beis Yosef (YD 63 DH Basar): The Tur holds that the Rosh holds like the Rashbam, since he brought his opinion last.
Note: Even though the Rosh initially said 'we hold like Rav', he was merely citing the Rif verbatim.
Poskim
Shulchan Aruch (YD 63:1): Chachamim forbade all meat that is found, whether in the market or in a Nochri's hand, even though all the sellers and all the Shochtim are Yisre'elim.
Beis Yosef (DH ul'Inyan): Since the Rif and Rambam agree, we forbid meat that was not watched if one has no Siman or recognition, unless it was hung on a nail so that a Sheretz could not take it and put back (other meat).
Levush (1): Chachamim forbade even if one saw the Nochri buy from a Yisrael, lest he sold to him a Neveilah or Tereifah. Some permit if he saw. This is the custom.
Rebuttal (Shach 5): The Shulchan Aruch connotes that it is forbidden even if it is found in a Nochri's hand. If so, this is even if we know that he bought it from a Yisrael. If there is concern lest the Yisrael sold to him a Tereifah, why do some permit if we saw him buy? Rather, we must discuss (buying from) Yisre'elim who sell only Kosher animals. The Levush holds that the stringent opinion is concerned lest he happened to sell a Tereifah to him. The primary reason is like the Magid Mishneh said, due to meat that was not watched. When most sell Vadai Kosher meat, one need not see (from whom the Nochri bought it). We follow the majority. We permit meat found in a Nochri's hand only when he did not see the Nochri buy it. (If he saw him buy it, it is a Kavu'a (fixed) Safek, and one may not rely on the majority - PF.)
Gra (1): The Shulchan Aruch cites the Rambam, who forbids even meat in a Nochri's hand. The Yerushalmi says that Rav forbids this. The Rambam relied on this, even though it is against the Bavli, like he often does.
Shulchan Aruch (ibid.): Further, even one who bought meat and put it in his house and it was left unwatched, it is forbidden, unless he had a Siman in it or recognized that this is surely it, or it was wrapped and sealed.
Beis Yosef (DH Basar): Rashi says that if meat was not watched Sha'ah Achas (a short time), even if it was on his table, Rav forbids it, lest it was switched with Neveilah, e.g. through ravens. What is found in a Nochri's hand is different, for it is Muchzak to be guarded.
Shulchan Aruch (2): Some permit meat that was not watched if he found it where he left it.
Rema: The custom is to be lenient like the latter opinion, even if it is in a Nochri's hand in a place where all the sellers are Yisraelim who sell Kosher meat.