In Mishnah 1, we learned that the Pesach offering is an exception: one that is slaughtered not for its own sake - meaning the slaughterer had the intention for a different type of offering - is not merely disqualified from fulfilling the owner's obligation, but is completely invalid. However, the Mishnah qualified the law and established that this is only "in its time." We must clarify, therefore, what that timeframe is, and on this point the Tannaim disagreed.
The Definition of "In Its Time":
No one disputes that the time for bringing the Pesach offering is in the afternoon, after midday on the fourteenth of Nisan. Nevertheless, there is a rule that "a portion of the day is like the whole day" - meaning that part of the day is considered like the entire day. Hence the dispute: is it specifically the afternoon of the fourteenth, or the entire day of the fourteenth.
In the words of the Mishnah: "HaPesach sheshachto beshacharis be'arba'ah asar shelo lishmo" - a Pesach offering was slaughtered on the morning of the fourteenth, and during its slaughter, they intended it for the sake of another offering:
"Rabbi Yehoshua machshir" - it is as if it were slaughtered on the thirteenth. The offering is valid and its service may be continued, except that it does not function as a Pesach offering, since it is early, and it is continued as a Shelamim offering or the like. There is no difference between the morning of the fourteenth and the thirteenth, since the time for bringing the Pesach offering has not yet arrived.
"Uven Beseira poseil" - it is as if it were slaughtered in the afternoon. The offering is completely invalid, because the fourteenth is the day on which the Pesach offering is brought, and there is no difference regarding the invalidation between the morning and the afternoon.
Regarding the practical halachah, the Rishonim disagreed: many of them learned that the invalidation applies only in the afternoon, which is indeed the time for bringing the Pesach offering; but from the words of the Rambam it appears that the law applies throughout the entire day of the fourteenth.
The Approach of Shimon ben Azzai:
In the second part of the Mishnah, an additional approach is brought regarding the question of when "not for its own sake" invalidates: "Amar Shimon ben Azzai, mekubalani mipi shivim u'shenayim zaken" - he has a tradition from seventy-two elders. It is worth noting that the word "zaken" (elder) is used here in the singular, to hint that they ruled together unanimously, as one man.
"Bayom shehoshivu Rabbi Elazar ben Azaryah biyeshivah" - on the day that they appointed Rabbi Elazar ben Azaryah as the head of the Sanhedrin, to serve as the Nasi. As recalled from the story in Tractate Berachos (page 28) with Rabban Gamliel and Rabbi Yehoshua, where a sort of rebellion took place and they deposed Rabban Gamliel from his presidency. The Gemara concludes there that although he did not serve as Nasi for a period, he did not leave the yeshivah and participated with the Sages. However, from this Mishnah, the Rashash proves that he was removed from the Sanhedrin entirely, since the rule is "we ascend in holiness and do not descend," and he would not sit in the Sanhedrin as a junior member after having been at its head. For this reason, he was present in the Beis Midrash, but not as part of the Sanhedrin.
Therefore, there were seventy elders there, and with the addition of the head of the Sanhedrin - seventy-one, and with Rabban Gamliel - seventy-two. All of them agreed unanimously, testifies Shimon ben Azzai, that the following principle is the guiding rule.
Ben Azzai admits that the Chatas and the Pesach in its time are the exceptions, but he wishes to add to them even the Olah, the burnt offering. For this purpose, he divides the offerings into two fundamental categories - those that are eaten and those that are not eaten:
That which is not eaten: The Olah, which is burned completely.
Those which are eaten: The Chatas, Asham, Shelamim, Todah, Maaser, Bechor and Pesach - their meat is eaten by the kohanim, by the owners, or by both.
From this he understands that the olah is a separate category and its law is different: in addition to the chatas and the pesach in its designated time, even the olah that was brought not for its own sake is completely invalid, and not just that it does not fulfill the owner's obligation.
In the words of the Mishnah: "Mekubalani mipi shivim ushnayim zakein beyom shehoshivu es Rabbi Elazar ben Azaryah biyeshivah, shekol hazevachim hane'echalim shenizbechu shelo lishman kesheirim" - I have received a tradition from seventy-two elders on the day they seated Rabbi Elazar ben Azaryah in the yeshivah, that all slaughtered offerings that are eaten which were slaughtered not for their own sake are valid, meaning that the seven offerings that are eaten are valid, "ela shelo alu labe'alim mishum chovah" - but they do not fulfill the owner's obligation - the owners who bring them do not fulfill their obligation with them, "chutz min hapesach umin hachatas" - except for the pesach and the chatas - where we have said that they are completely invalid.
The Mishnah explicitly continues: "Velo hosif Ben Azai ela ha'olah" - and Ben Azai only added the olah - the only addition Ben Azai makes to the opinion of the Tanna Kamma is the olah offering, whose law is like the chatas and the pesach in its designated time. "Velo hodu lo Chachamim" - and the Sages did not agree with him - even though he had a tradition, the Sages did not accept it, and therefore the halachah follows the opinion of the Tanna Kamma above.
A technical point in conclusion:
In practice, in the list of offerings that are not eaten, in addition to the olah, one must also add the inner chatas offerings - chatas offerings whose blood is sprinkled inside, in the Holy or the Holy of Holies, and their meat is burned and not eaten at all. There are five of them:
The he-goat of Yom Kippur, for Hashem.
The bull of the Kohen Gadol on Yom Kippur.
The bull for an unwitting communal sin (par he'elem davar).
The bull of the anointed kohen (as remembered from Tractate Horayos).
The communal he-goat for idol worship.
However, the Mishnah did not need to mention them, because it was already stated that a chatas is completely invalid, and these too are chatas offerings, and there is no dispute regarding them: the Tanna Kamma holds that the chatas is invalid, and Ben Azai also holds that the inner chatas offerings are invalid, and there is no difference between them. Nevertheless, in terms of the fundamental division between those that are eaten and those that are not eaten, the olah and the inner chatas offerings are the ones that are not eaten.