1) HOW A "TAM" CAN BECOME A "MU'AD"
QUESTIONS: The Mishnah teaches that even a Shor Tam that kills a person is put to death. A Shor Mu'ad that kills a person is put to death and, in addition, the owner must pay Kofer. The Gemara asks that if a Shor Tam is put to death for killing a person, how can a Shor Tam ever become a Mu'ad? Since the Shor is put to death the first time that it kills a person, it will never be able to kill a person three times.
The Amora'im suggest various answers to this question. Rav Acha explains that a Shor can become a Mu'ad to kill people if the first two sets of witnesses who testify that the Shor killed are made into Edim Zomemim, and after the third testimony that it killed a person, the Mazimim of the first two sets of witnesses are proven to have been lying and the earlier sets of witnesses are vindicated.
The Gemara asks that this answer suffices only according to the opinion that "Yi'udei Tora." According to that opinion, if witnesses testify that the animal gored three times in the past, the Shor becomes a Mu'ad even though the owner found out about the first three gorings at one time. According to the opinion that "Yi'udei Gavra," however, the owner must be warned on three different days in order for the Shor to become a Mu'ad. He must have the opportunity to guard his Shor after each time that Beis Din warns him, for otherwise his Shor does not become a Mu'ad. In the case of the Gemara, when the Mazimim are proven to be lying Beis Din accepts the testimony about all three gorings at the same time, and thus the Shor should not become a Mu'ad according to the opinion that "Yi'udei Gavra"!
The Gemara answers that the witnesses testify that the owner was present on each occasion that his Shor gored. This answer implies that even if Beis Din did not warn the owner to guard his Shor on three occasions, but the owner knew on his own to guard his Shor based on three different events which he saw for himself, it suffices to make the Shor a Mu'ad even according to the opinion of "Yi'udei Gavra."
RASHI here explains that when the witnesses testified about the gorings, the owner becomes obligated to pay Nezek Shalem for the third goring. The Gemara refers to a case in which the Mazimim were proven to be lying after the third goring, and the owner thus immediately pays Nezek Shalem for the third goring. Rashi here is consistent with his opinion expressed earlier (23b, DH v'Lo).
Tosfos and the other Rishonim argue that even those who maintain "Yi'udei Tora" require that the owner know that the animal became a Mu'ad prior to the Negichah which obligates him to pay Nezek Shalem. They explain that only on the fourth Negichah does the owner pay Nezek Shalem for the damage of a Mu'ad. (See Insights to 24:1.)
According to Rashi, clearly the Gemara's original question -- how can a Shor Tam ever become a Mu'ad -- is valid only according to the opinion of "Yi'udei Gavra," because according to the opinion of "Yi'udei Tora" it is obvious how a Shor Tam can become a Mu'ad: no one testified about the first gorings until after it had gored a third time, at which point three sets of witnesses came to testify about the three gorings. In such a case, according to the opinion of "Yi'udei Tora" the Shor immediately becomes a Mu'ad. (GILYON TOSFOS cited by the Shitah Mekubetzes)
(a) However, if it suffices -- even according to the opinion of "Yi'udei Gavra" -- for the owner to witness the goring on three occasions in order to make his Shor into a Mu'ad, then why does the Gemara not answer simply that three sets of witnesses came on the same day to testify about three gorings, and each set testifies that the owner himself saw the goring? Why is it necessary to present a case where the witnesses became Zomemim and later became vindicated?
Even according to Tosfos, it is clear from the Sugya that if the owner witnessed the gorings, even if Beis Din finds out that the Shor gored four times only on the same day (i.e. the day on which the Mazimim were proven to be lying), the Shor is put to death. If a further Negichah is required, the Gemara's question will remain: how will there ever be a case of Kofer if the animal is put to death (for its earlier gorings)? (See TOSFOS RABEINU PERETZ.) Why, then, is it necessary to say that the case is one of Zomemim? (See SHITAH MEKUBETZES in the name of TOSFOS RABEINU PERETZ. The Shitah Mekubetzes cites GILYON TOSFOS who suggests that Rav Acha indeed changed his mind and concluded that the case does not have to involve Zomemei Zomemim. However, this is not the simple meaning of the Gemara.)
(b) RASHI (DH Gabei) explains that the last set of witnesses -- the witnesses who proved the Mazimim to be liars and who vindicated the earlier sets -- was the set that testifies that the owner saw the gorings. Why does Rashi say that it was the last set that testifies that the owner saw the gorings? Why does he not explain that it was the original sets of witnesses who say that the owner saw the gorings? (TORAS CHAIM)
In fact, the RE'AH in the Shitah Mekubetzes explains that it was the first sets of witnesses who testified that the owner was present.
ANSWERS:
(a) The Gemara does not mean to say that if the owner saw the gorings, it suffices to make the Shor a Mu'ad, according to the opinion of "Yi'udei Gavra." Seeing the goring is not enough to obligate the owner to guard the Shor better; the owner must be warned by Beis Din (who heard testimony that the Shor gored) to guard his Shor. However, in the case of Edim Zomemim, the owner was warned by Beis Din to guard his Shor (before the witnesses became Zomemim). The only reason why the owner might not be required to heed that warning is that the witnesses turned out to be Zomemim, and thus the owner can say that Beis Din was mistaken and thus he did not take their warning seriously. If, however, the owner was present when the Shor gored and he knew that the original witnesses were telling the truth (and that they really did see the goring), he has no right to disregard Beis Din's warning to him; he should have anticipated that the Mazimim would be proven false at a later time! That is why the Gemara explains that the witnesses became Zomemim, according to the opinion of "Yi'udei Gavra."
(This seems to be the intention of the answer of TOSFOS RABEINU PERETZ.)
(b) Rashi needs to explain that the final pair of witnesses testified to the owner's presence at the gorings, because the first pair's testimony with regard to the owner's presence would not have been believed. The reason for this is as follows: If they testified, before they became Zomemim, that the owner saw the goring, Beis Din will not accept that as part of their testimony because it is immaterial to the case (i.e. to the monetary obligation which is the subject of their testimony) whether or not the owner saw the goring. The only time the owner's presence is necessary is after the pair of Mazimim witnesses are proven to be liars, and Beis Din needs to know whether the owner knew all along that the original witnesses were telling the truth (and therefore the owner had to heed the warnings that Beis Din gave him after the testimony of the original witnesses). The first set of witnesses would not be believed to present such testimony since they would be biased ("Noge'a b'Davar") -- first, because they are saying that the owner saw them (i.e. they are testifying about something about themselves), and second, because without this latter testimony about the owner, their original testimony would not have Halachic validity. Therefore, it must have been the last set of witnesses that testified that the owner was present at the gorings.
2) THE "ISUR ACHILAH" OF A "SHOR HA'NISKAL"
QUESTION: The Beraisa derives from the verse, "Lo Ye'achel Es Besaro" (Shemos 21:28) that a Shor Mu'ad becomes forbidden to be eaten (Asur b'Achilah) after Beis Din passes the verdict (Gemar Din) that it must be stoned, even before it is actually stoned (Sekilah). If the verse intended to teach that it is Asur b'Achilah only after it is stoned, it would be extraneous; any animal that dies without proper slaughter may not be eaten. The Gemara asks that perhaps the verse of "Lo Ye'achel" indeed refers to after the animal was stoned, but it is not teaching that the animal is Asur b'Achilah but that it is Asur b'Hana'ah, since whenever the Torah says "Lo Ye'achel" it includes an Isur Hana'ah, as Rebbi Avahu teaches.
The Gemara suggests two answers to this question. If the verse intended to make the animal Asur b'Hana'ah after Sekilah, it would have said, "Lo Yehaneh," since it is teaching only an Isur Hana'ah and not an Isur Achilah. Alternatively, the verse should have said "Lo Ye'achel" without adding the words "Es Besaro." It must be that the verse is teaching an Isur Achilah for eating meat that would otherwise be permitted to eat, and therefore it must be referring to the animal before the animal is stoned.
The second answer of the Gemara seems to reject the first answer. It seems to maintain that even if the verse teaches only an Isur Hana'ah, it is justified in saying "Lo Ye'achel" (and not "Lo Yehaneh"). Why, then, does RASHI (DH Es Besaro) write that according to the second answer of the Gemara, it is only because the verse prohibits the animal b'Achilah before Sekilah that the verse is justified in using the words "Lo Ye'achel"? Rashi should say instead that according to the second answer, the Isur Achilah is derived from the words "Es Besaro" and has nothing to do with the words "Lo Ye'achel"! (PNEI YEHOSHUA)
ANSWER: The Beraisa which the Gemara explains uses the following wording when it proves from "Lo Ye'achel" that the Shor is Asur b'Hana'ah before Sekilah: "Do we not know already that a Neveilah is Asur b'Achilah? Why, then, does the Torah say 'Lo Ye'achel?'" What bothered Rashi was that this does not seem to conform with the second answer of the Gemara. According to that answer, the inference from the verse is not that the words "Lo Ye'achel" are extraneous, but that the verse adds two extra words which imply that it refers to when one slaughters the Shor ha'Niskal before it is stoned. Therefore, Rashi found it necessary to explain that even according to the second answer the inference from the verse is from the words "Lo Ye'achel."
Rashi's intention is that the words "Es Besaro" alone do not imply that there is an Isur Achilah and not an Isur Hana'ah. The reason for this is connected to the way an Isur Hana'ah is inferred from the words "Lo Ye'achel." Why is it that whenever the verse says "Lo Ye'achel" an Isur Hana'ah is implied? After all, the verse says only an Isur Achilah. The answer is that according to Rebbi Avahu, the verse mentions Achilah only as a sample of the type of Hana'ah that is prohibited. It means that just as the Hana'ah of Achilah is prohibited, every type of Hana'ah is prohibited. Hence, the words "Es Besaro" do not add anything more than the words "Lo Ye'achel"; perhaps the verse merely gives Achilah ("Es Besaro") as an example of the Isur Hana'ah and its main intent is to prohibit the animal b'Hana'ah (all Hana'ah) after Sekilah. The only way to infer that the verse is indeed creating a new Isur of Achilah is from the fact that the verse offers two phrases which prohibit specifically Achilah -- "Lo Ye'achel" and "Es Besaro" (the benefit normally derived from meat is Achilah). The Gemara is saying that even if the Torah would write a single phrase of Achilah when its main intent is to create an Isur Hana'ah, it would not emphasize the Achilah a second time unless it indeed intended to create a new Isur Achilah (i.e. to prohibit eating something that would have been permitted to eat without the verse). (M. Kornfeld, based on the PNEI YEHOSHUA here and HA'MIKNAH to Kidushin 56a)