1) "MAI SHAYAR D'HAI SHAYAR" -- WHAT DID THE TANA LEAVE OUT
QUESTION: Rebbi Acha bar Chanina says that when multiple Korbenos Musaf are offered, a separate Shir is recited for each one, and a separate set of Teki'os is sounded for each one.
The Gemara asks several questions on Rebbi Acha's opinion. One question is based on the Mishnah (53b) which lists only one day on which 48 Teki'os are sounded in the Mikdash -- Chol ha'Mo'ed Sukos which occurs on Erev Shabbos. According to Rebbi Acha, the Mishnah should also mention Rosh Hashanah which occurs on Shabbos, since on that day, too, 48 Teki'os are sounded (the 21 Teki'os of every day, and an additional 27 Teki'os for the three different Musaf offerings offered on that day). The Gemara answers that the Tana simply left out that case. The Gemara asks, "What else did the Tana leave out?" -- "Mai Shayar d'Hai Shayar" (literally, "What [else] did the Tana leave out that he [also] leaves out this"). The Gemara's question is based on the rule that whenever the Tana omits something from a list, he omits more than just one case.
The Gemara answers that the Tana also omitted Erev Pesach, on which an additional 27 Teki'os are sounded (9 for each of the 3 groups into which the Jewish people are divided when they bring the Korban Pesach). However, the Gemara eventually rejects this answer and says that the case of Erev Pesach is not considered a case which the Tana omitted, because the Tana of the Mishnah may follow the view of Rebbi Yehudah with regard to Erev Pesach. Rebbi Yehudah maintains that the last of the three groups on Erev Pesach did not complete the recitation of Hallel even once, and thus only one set of Teki'os, at most, was sounded for them. Consequently, according to Rebbi Yehudah the maximum number of Teki'os on Erev Pesach is only 42 (21 normal Teki'os, 9 for the first group, 9 for the second group, and 3 for the third group).
The Gemara answers that even if the Mishnah follows the view of Rebbi Yehudah, there still exists another case which it omitted. On Erev Pesach that falls on Erev Shabbos, 48 Teki'os are sounded even according to Rebbi Yehudah (42 as described above, 3 to warn the people to abstain from Melachah, and 3 to announce the onset of Shabbos). Accordingly, the Mishnah does not contradict Rebbi Acha, because it left out several cases.
Why does the Gemara reject its original answer for Rebbi Acha by asserting that the Mishnah follows Rebbi Yehudah? What forces the Gemara to say that the Mishnah follows Rebbi Yehudah? The Gemara should answer simply that the Mishnah follows the Rabanan who argue with Rebbi Yehudah and maintain that Erev Pesach indeed has 48 Teki'os, and that is the additional case which the Mishnah left out, in addition to the case of Rosh Hashanah that occurs on Shabbos. Why does the Gemara insist that the Mishnah follows Rebbi Yehudah?
(a) The RA'AVAD (cited by the SHITAH MEKUBETZES to Bava Kama 15a) and the RITVA offer a novel explanation for the phrase that the Gemara often uses, "What else did the Tana leave out?" The accepted meaning of, "Mai Shayar d'Hai Shayar," is that it is not the manner of the Tana to leave out just one case from a list of cases; the Tana leaves something out only when there are two or more cases to leave out. This is how Rashi seems to explain this expression in Ta'anis (13b, DH Mai).
The Ra'avad and Ritva write that this is not the correct meaning of the phrase. Rather, "Mai Shayar d'Hai Shayar" is a rhetorical question, a declaration that we may not assume that the Tana omitted anything. The only valid way to propose that the Tana omitted a case is by proving that the Tana did not intend to list every case. This can be proven by demonstrating that there is at least one other case which the Tana indisputably omitted even though it belongs on his list. That unquestionable omission shows that the Tana did not intend to list every case, and thus we may assume that the Tana also omitted the case in question.
Accordingly, the only way to prove that the Mishnah here omitted the case of Rosh Hashanah that occurs on Shabbos is by demonstrating that the Mishnah definitely omitted another case. The Gemara suggests that the Mishnah left out Erev Pesach. It responds that this does not prove conclusively that the Tana did not intend to list every case, because it is possible that the Mishnah follows the opinion of Rebbi Yehudah and the case of Erev Pesach is not an omission.
(b) The SEFAS EMES explains that the expression, "Mai Shayar d'Hai Shayar," can be understood in the usual sense. He explains the Gemara as follows.
In general, why does a Tana not omit one case from his list? The Tana is concerned that his words will be misunderstood; people might think that his list is comprehensive and that he omitted nothing (as a consequence, they will assume that the case which the Tana omitted was omitted because it does not belong in the list). In order to prevent incorrect conclusions from being drawn, when the Tana intends to omit a certain case, he omits a number of cases so that everyone will know that his list is not exhaustive.
The Gemara here says that just as it is not the manner of the Tana to omit one case alone (when he omits no other case), it is also not the manner of the Tana to omit a case when that case is subject to a Machlokes Tana'im. The Tana does not leave out such a case for the same reason he does not omit a single case: the Tana is concerned that he will be misunderstood. If he omits a case which is subject to a Machlokes Tana'im, people might think that the reason he omitted that case is because he rules like the Tana who maintains that the case does not belong in the list at all. Therefore, if such a case really belongs in the list, the Tana certainly will include it in order to avoid such a misunderstanding.