(Mishnah): (One is exempt for offering outside the Mikdash) a Ba'al Mum... for Oso v'Es Beno...

Oso v'Es Beno teaches that Chachamim exempt not only for what is intrinsically forbidden, rather, even for what is forbidden due to something else (the Shechitah of its mother or child).

Chulin 78a (Mishnah): If a mother and her child were slaughtered on the same day, both animals are Kosher.

82a (Mishnah): If Oso v'Es Beno were sold to two people, the first buyer slaughters first (i.e. today). If the second slaughtered first, he was zealous and profits.

(Beraisa): If the second slaughtered first, he was zealous and gained. He was zealous to avoid transgressing, and he gained, i.e. he may eat the meat today.

114b (Rav Ashi): The source to forbid eating meat and milk is "Lo Sochal Kol To'evah (do not eat any abomination)" - anything that the Torah forbade doing, one may not eat the result.

115a - Suggestion: If Oso v'Es Beno are slaughtered on the same day, the latter should be forbidden! (It was slaughtered b'Isur.)

Rejection: The Torah forbids Mechusar Zeman (something that is not ready yet) to the Mizbe'ach. We infer that it is permitted to people.

Rambam (Hilchos Shechitah 12:1): If one slaughtered Oso v'Es Beno on one day, he may eat the meat.

Rosh (Chulin 5:5): Bahag says that one who slaughters Oso v'Es Beno on the same day may not eat the latter that day. Raboseinu say that he learned from the Beraisa that says that if the second slaughtered first, he was zealous to avoid transgressing, and he gained, i.e. he may eat the meat today. We infer that if he did not slaughter first, he transgressed, and he may not eat. If he does not slaughter after the first (on the same day), he did not transgress! If he slaughtered after the first and transgressed, he may eat! How can we find together that he transgressed and he may not eat? Rather, we must say that if he slaughtered second, he may not eat the meat that day.

Divrei Chamudos (10): Bahag agrees that Chulin 115 proves that one may eat the meat, i.e. mid'Oraisa. He makes a fine mid'Rabanan, like the Ran (below) says. The text of Bahag says that whether he was Shogeg or Mezid, the same fine applies - 'he leaves the meat until evening'. He does not distinguish between the Shochet (the one who slaughtered) and others. The different laws of one who did Melachah on Shabbos apply also here. The Rosh holds that it is not a fine. Rather, Chachamim wanted to be stringent. If so, surely the laws of Melachah on Shabbos apply here!

Ran (27a DH Chulin): Rashi says that there was no Chidush to say that when the latter was Chulin outside the Mikdash, both are Kosher. It is for parallel structure with the other cases. Tosfos says that there was a Hava Amina that the latter is forbidden, due to Lo Sochal Kol To'evah. The Mishnah teaches that this is not so, for the reason given on 115a. Since the Torah forbids Mechusar Zeman to the Mizbe'ach, we infer that it is permitted to people. Bahag forbids eating the second that day. This is a fine. He learned from actions done on Shabbos (one may not benefit from them on Shabbos).

Shulchan Aruch (YD 16:3): If one transgressed and slaughtered Oso v'Es Beno on one day, he may eat them. Some forbid (Rema - on that day, to eat the latter one slaughtered).

Prishah (4): Bahag learns from laws of Shabbos. One should not benefit from Isur. If so, it is forbidden even to others, like regarding Shabbos (OC 318:1). However, even Bahag can hold like the Gemara said, that since the Torah forbids Mechusar Zeman for Avodah, we infer that it is permitted to commoners. It is improper to forbid it, so we forbid it only to the Shochet. It is unreasonable to fine others due to his transgression, since the action itself is not a reason to forbid. This is unlike cooking on Shabbos. There, letter of the law even b'Shogeg he and others should not benefit from Melachah done on Shabbos. We must distinguish these. If one cooked on Shabbos, it is forbidden to him permanently. Here we forbid only the same day, even if he was Mezid. Since cooking on Shabbos is forbidden letter of the law, and Chachamim saw that it is proper to fine him, there is no reason to forbid him to eat it that day, but permit another day. Therefore, he is forbidden forever. Here, the Shechitah itself is not forbidden, only he may not slaughter today. Therefore, Chachamim forbid him only on that day that he wanted to benefit from it.

Bach (DH u'Mah she'Chosav): Bahag forbids only the latter animal. I say that he explains that 115a suggested that the latter should be forbidden forever, because an Isur was done. Rashi explains the question about Shilu'ach ha'Kan like this. It answered that since the Torah forbade Mechusar Zeman for Avodah, we infer that it is permitted to people. Therefore, it is not forbidden forever. However, surely it is forbidden that day due to Lo Sochal Kol To'evah. Since it was despised to slaughter it that day, one may not eat it that day. The Rosh says that one may infer from the Beraisa 'he was zealous and he gained.' It seems that the Rosh holds like this. We rule like this.

Taz (3): Since the Torah forbids Mechusar Zeman for Avodah, i.e. an animal before its eighth day, this implies that it is permitted to commoners. The latter opinion, Bahag, fines to forbid it that day, just like we fine one who cooked on Shabbos. The Gemara only excluded a permanent Isur, but it is forbidden that day due to "Lo Sochal Kol To'evah."

Mishneh l'Melech (Hilchos Isurei Mizbe'ach 3:8): The Pri Chodosh (and Levush and Taz - Mishbetzos Zahav) explains that the Torah forbade Mechusar Zeman, i.e. an animal before eight days, for Avodah, so we infer that it is permitted to a commoner. We must say that we know that it was born after a full term pregnancy. If not, it is forbidden due to a Safek Nefel! The Gemara asked that Oso v'Es Beno should be forbidden due to "Lo Sochal Kol To'evah." How did we answer from Mechusar Zeman, in which no Aveirah was done?! Rather, 'Mechusar Zeman for Avodah' refers to Oso v'Es Beno. A verse teaches that it applies to Kodshim (78a). If Oso v'Es Beno were forbidden to people, we would know that it is Pasul for Kodshim, for it is not "mi'Mashkeh Yisrael"!

Note: Even though "mi'Mashkeh Yisrael" is a verse in Yechezkeil, we must say that before he wrote the verse, it was a tradition (Sanhedrin 22b). Menachos 6a asks why we need other verses to disqualify a Tereifah for Avodah, since we could learn from "mi'Mashke Yisrael"!

Shach (3): The first animal is permitted, for when he slaughtered it, he did not transgress. The Ran explains that it is a fine to forbid the latter, like one who cooked on Shabbos. It seems that we fine only him, like the Prishah connotes. Also the Rosh says like this, and this follows from the proof he brought from Rav Yosef (the Beraisa).

Sifsei Da'as: The proof from Rav Yosef is only regarding the Shochet, but not regarding others. See Tevu'as Shor 7. We hold like Bahag. All the Acharonim ruled like him. It seems that even if he was Mezid, it is forbidden to him and permitted to others. The Bach holds that Bahag forbids mid'Oraisa. The Acharonim say that it is only a fine mid'Rabanan. Yad Eliyahu says that Maharimat asked why Shechitah on Shabbos permits. We should say 'if he transgressed, it did not help'! We can ask similarly, here. The same answer applies. The action is intrinsically permitted; it is forbidden only on this day, therefore, 'if he transgressed, it did not help' does not apply. In any case, this is not difficult. Since the Torah forbids Mechusar Zeman for Avodah, this implies that it is permitted to commoners.

Tevu'as Shor (7): It is forbidden even to others on that day, so his evil act will not help. At night it is permitted even to him. This is unlike Shabbos, which is punishable by stoning; there, we forbid permanently to him. It is unlike other Isurim.

Sifsei Da'as: Tevu'as Shor asked why if one was Mevatel Isur l'Chatchilah, it is permitted to others. He holds that we fine anyone who transgressed mid'Oraisa, lest he benefit from his sin. If it would be forbidden to others, it would be permanently forbidden, and more stringent than Shabbos. Rather, since it is only in order that one not benefit from sin, regarding Shabbos we permit on Motza'ei Shabbos, and he did not benefit from Melachah on Shabbos. We forbid him, because Shabbos is (very stringent, i.e.) punishable by stoning. For other Aveiros, we fine him and others not to benefit from the Aveirah. One who was Mevatel an Isur transgressed only mid'Rabanan. The Ra'avad holds that the Torah forbids to be Mevatel Isur. Even so, the Rashba says that the Ra'avad permits to others, like the Shach (99:7) says, even though there is benefit from the Aveirah. Siman 99 connotes that if one was Mevatel an Isur mid'Rabanan, it is forbidden to him himself. Here the Mechaber does not forbid even the same day, even though it is an Isur Torah. This is unlike being Mevatel an Isur. There, we fine him lest he do so again. Regarding Oso v'Es Beno, being able to eat this day is not a reason for him to do so again. (I.e. there is no reason to expect that a case of Oso v'Es Beno will occur for him again). We make such a distinction between here and Siman 110; we do not decree lest one take from a mixture (of Rov Heter) in a Kavu'a way (so it is considered an even Safek).

Tevu'as Shor (1 and Simlah Chadash 3): If two slaughtered at once, both transgressed, and they are forbidden that day, even though one of them finished first, since Shechitah is from the beginning to the end.

Pri Megadim: Keneses ha'Gedolah brings that Dameshek Eliezer explains that Bahag forbids both animals to the latter Shochet, and the latter animal to the first Shochet. This is unreasonable; the Acharonim connote otherwise. Why should the first animal be forbidden to the latter Shochet? It was permitted when it was slaughtered!

Gra (6): Bahag explains that the Mishnah says that both are Kosher, i.e. mid'Oraisa, and even mid'Rabanan after that day.

Pischei Teshuvah (2): Zichron Yitzchak says that if the father and its son were slaughtered in one day, one may eat (even) the latter that day, since it is a Safek whether the Isur applies to the father, and it is a Safek whether the Halachah follows Bahag. Even though a Sefek-Sefeka does not help for Davar she'Yesh Lo Matirim (it will be permitted in another time or situation), since it is not forbidden to all, rather, only to the Shochet, we do not consider this Davar she'Yesh Lo Matirim, like the Maharshal (Yevamos 8:34). I say that we do not rule like the Maharshal, for we hold (Rema 102:4) that if one vowed not to eat something, it is considered Davar she'Yesh Lo Matirim, even if it is forbidden only to the one who vowed.

Sifsei Da'as (102:2): Keneses ha'Gedolah says that something not forbidden to all is not considered Davar she'Yesh Lo Matirim. He learns from R. Asher of Lunil in Tamim De'im 120, who is lenient about a Safek about something brought from outside the Techum for Ploni, since it is forbidden only to Ploni. The Shulchan Aruch (OC 325:8) is stringent about this, like the Rif!