1) CHANUKAH AND "SHEMEN SEREIFAH"
QUESTION: Why does the Gemara interrupt its discussion of Chanukah to discuss the prohibition of lighting the Shabbos candles with the Sugya of "Shemen Sereifah" (Terumah oil that became Tamei and must be burned)?
(a) The RASHBA (end of 23b) in the name of RABEINU YONAH and the CHIDUSHEI HA'RAN explain that the Sugya of Shemen Sereifah is relevant to the laws of Chanukah. Rabah and Rav Chisda (23b) argue concerning the reason why one may not light the Shabbos candles with Shemen Sereifah. Rabah says that it is because of the fear that one might tilt the lamp to hasten the burning process. Rav Chisda says that it is because the Mishnah is referring to a case in which Yom Tov falls on Friday, and lighting with Shemen Sereifah is forbidden on Yom Tov.
Consequently, this discussion is also relevant to the laws of Chanukah. When Shabbos and Chanukah coincide, may one use Shemen Sereifah for the Chanukah lights on Friday evening? Even if we conclude that it is permitted to use all of the other inferior oils on Chanukah (because "Kavsah Ein Zakuk Lah" and "Asur l'Hishtamesh l'Orah"), using Shemen Sereifah should still be prohibited according to Rabah because of a different concern -- perhaps one will tilt the lamp on Shabbos in order to hasten the burning process. Therefore, the discussion of Shemen Sereifah is interjected here in the Gemara.
The MAHARATZ CHAYOS adds that according to Rabah, one is not permitted to burn Shemen Sereifah even on a weeknight of Chanukah. Since Rabah maintains that there is a fear that one might tilt the lamp to speed up the burning of the oil, we are concerned that one might consequently cause the amount of oil in the Chanukah lamp to diminish to less than the amount required to remain burning for the proper length of time.
(b) The RASHASH says that the discussion of Shemen Sereifah is interjected here for the opposite reason. According to Rav Chisda's reason for not lighting the Shabbos candles with Shemen Sereifah, the discussion of Shemen Sereifah is not relevant at all to Chanukah. Therefore, the Gemara waited until after the discussion of kindling the wicks and lights of Chanukah to discuss Shemen Sereifah. After it discusses the Chanukah lights, the Gemara returns to the Mishnah and discusses this Halachah (which also involves wicks and lights). Afterwards, the Gemara returns to address the laws of Chanukah which are unrelated to the kindling of the Chanukah lights. (Since the laws of Chanukah are discussed nowhere else in the Gemara, they are discussed here as an addendum to the laws of the wicks and oils that may be used.)
2) SAYING "AL HA'NISIM" IN BIRKAS HA'MAZON
QUESTION: The Gemara asks whether we recite "Al ha'Nisim" in Birkas ha'Mazon on Chanukah. Both RASHI and TOSFOS explain that the Gemara does not ask whether we recite "Al ha'Nisim" in Shemoneh Esreh, because it is obvious to the Gemara that we do (as Rav Sheshes says at the end of the Sugya). Rashi and Tosfos seem to argue, though, about why we recite "Al ha'Nisim" in Shemoneh Esreh.
Rashi says that we recite "Al ha'Nisim" in Shemoneh Esreh because "[the days of Chanukah] were established as days of praise and thanksgiving, as the Gemara said earlier (21b)" (and therefore it is obvious that we make mention of Chanukah in our Shemoneh Esreh).
Tosfos, however, says that it is because "Shemoneh Esreh is recited in public, where there is Pirsum Nes (publicizing the miracle of Chanukah), and thus Al ha'Nisim is recited. But Birkas ha'Mazon is recited individually in one's home where there is no Pirsum Nes."
Furthermore, Rashi and Tosfos argue about another point. In the end of the Sugya, Rav Sheshes says, "Just like Al ha'Nisim is recited in the Hoda'ah (thanksgiving) section of Shemoneh Esreh, so, too, it is recited in the Hoda'ah section of Birkas ha'Mazon."
Rashi explains that the reason why "Al ha'Nisim" is mentioned in the Hoda'ah section of Birkas ha'Mazon (and Shemoneh Esreh) is because the entire institution of Chanukah is for the sake of giving thanks (Hoda'ah), and thus, naturally, we recite "Al ha'Nisim" in the blessing of giving thanks.
Tosfos, however, writes that we recite "Al ha'Nisim" in Hoda'ah because the style of the "Al ha'Nisim" addition is that of thanksgiving (thanking Hash-m) and not of prayer (making requests of Hash-m). Had it been written in the style of a prayer, it indeed would have been placed in "Boneh Yerushalayim," where all other special days are mentioned. What is the basis of the argument between Rashi and Tosfos?
ANSWER: When the Gemara answers, "If one wants to say Al ha'Nisim, he may say it in Hoda'ah," Tosfos understands that the reason to say "Al ha'Nisim" is the same reason for saying any other special paragraph for a special day (like Shabbos, Rosh Chodesh, or Yom Tov); the Rabanan established that on special days, one should make mention of that day in Birkas ha'Mazon.
Rashi, on the other hand, understands that the Gemara's reason for saying "Al ha'Nisim" is not because of the concept of making mention of the special day in Birkas ha'Mazon (because we make mention only of festivals that are mid'Oraisa, and Chanukah is mid'Rabanan). Rather, the reason for saying "Al ha'Nisim" in Birkas ha'Mazon is because of the unique obligation to give thanks to Hash-m on Chanukah (because that is the purpose of Chanukah, as the Gemara says earlier, "l'Hallel v'Hoda'ah").
This difference in understanding the essential nature of "Al ha'Nisim" explains why Rashi and Tosfos give different reasons for reciting it in Shemoneh Esreh, and different reasons for reciting it in the section of Hoda'ah. (RAV Y. D. HOMNICK in SEFER NACHALAS YAKOV)
3) HALACHAH: SAYING "AL HA'NISIM" IN BIRKAS HA'MAZON
QUESTION: The RAMBAM (Hilchos Berachos 2:6) rules that one says "Al ha'Nisim" in Birkas ha'Mazon. This is also the ruling of the SHULCHAN ARUCH (OC 682:1).
Why is saying "Al ha'Nisim" obligatory? The Gemara here implies that it is optional ("Rav Huna said that one does not mention Al ha'Nisim, but if one wants to mention it, he says it Hoda'ah")!
(a) The ROSH YOSEF gives three answers. First, the simple understanding of the statement of Rav Sheshes at the end of the Gemara is that he argues with Rav Huna and maintains that one must say "Al ha'Nisim" in Birkas ha'Mazon. This is how RABEINU CHANANEL understands the Gemara (although his text had the name "Rava" instead of "Rav Sheshes").
(b) Since the Jews accepted upon themselves to say "Al ha'Nisim" in Birkas ha'Mazon, it has become obligatory (similar to the way that the Shemoneh Esreh of Ma'ariv became obligatory).
(c) The Yerushalmi says that "Al ha'Nisim" is obligatory, and one who forgets to say it must repeat Birkas ha'Mazon. Since the Bavli and Yerushalmi are arguing, the Rambam rules that we must be stringent in accordance with the Yerushalmi and require that "Al ha'Nisim" be said in Birkas ha'Mazon. However, one does not repeat Birkas ha'Mazon if he forgets to say "Al ha'Nisim," because doing so would be a Berachah l'Vatalah according to the Bavli. (ROSH YOSEF in the name of the LECHEM MISHNEH)
4) MENTIONING ROSH CHODESH IN THE BLESSING OF THE HAFTARAH ON SHABBOS-ROSH CHODESH
QUESTION: The Gemara concludes that the Halachah is not like "all of these teachings," but rather like the teaching of Rebbi Yehoshua ben Levi who says that we mention Shabbos in the Ne'ilah prayer on Yom Kipur when Shabbos and Yom Kipur coincide. RASHI says that the Gemara is repudiating all of the previous statements, including that of Rav Gidal, who says that we do not mention Rosh Chodesh in the blessing after the Haftarah on Shabbos (when Shabbos and Rosh Chodesh coincide).
Why does Rashi say that Rav Gidal's ruling is also refuted? The ruling of Rebbi Yehoshua ben Levi does not conflict with the ruling of Rav Gidal! The reason why we mention Shabbos in Ne'ilah (Rebbi Yehoshua Ben Levi's ruling) is because of the concept of "Yom she'Chayav Bo Arba Tefilos" -- there are already several other Shemoneh Esreh's that one recites on Shabbos-Yom Kipur which must include mention of Shabbos (since they would be recited even if it was not Yom Kipur). Therefore, even though one recites Ne'ilah only because of Yom Kipur, one should still make mention of Shabbos. The Haftarah, however, is never read on Rosh Chodesh, so there is no reason to warrant mentioning Rosh Chodesh in the blessing of the Haftarah! (TOSFOS DH v'Leis)
(a) The ROSH (2:16) explains that once we are informed of the second statement of Rav (related to us in his name by Rav Achdevoy), in which it is clear that Rav does not agree with the concept of "Yom she'Chayav Bo Arba Tefilos," it is evident that Rav Gidal and Rav Achdevoy are not arguing, but are expressing the same opinion of Rav through two different cases. Consequently, it makes sense to say that once Rav Achdevoy's opinion is rejected, so, too, is Rav Gidal's.
(b) RASHI apparently understands that the Shemoneh Esreh of Ne'ilah is unlike any other Shemoneh Esreh. Ne'ilah is not in the category of ordinary Tefilos (which were instituted to correspond to the various Korbanos), but it is a completely new institution which was established as a way of concluding the fast. (Ne'ilah is not an "Avodah," but rather a "Gemar Tzom.") Therefore, since Shabbos has no connection with Ne'ilah because it is not a normal Shemoneh Esreh, this case is identical to the case of mentioning Rosh Chodesh in the Haftarah blessing (and since Rebbi Yehoshua ben Levi's ruling is in contrast to Rav Gidal's, Rav Gidal is refuted). (M. KORNFELD)
HALACHAH: According to Rashi's explanation of the Gemara, we do mention Rosh Chodesh in the blessing after the Haftarah on Shabbos (not like Rav Gidal). According to Tosfos' explanation, we do not mention Rosh Chodesh (like Rav Gidal).
Many Rishonim learn like Rashi (the Rif, Rabeinu Yonah, Rosh), but, as the Rosh writes, they limit the Halachah to mentioning Rosh Chodesh in the middle of the blessing, but not in the concluding blessing itself (the same way we mention "Ya'aleh v'Yavo" in the Shemoneh Esreh on Shabbos, but we do not make mention of it in the concluding blessing, "Baruch Atah Hash-m Mikdash ha'Shabbos").
The SHULCHAN ARUCH (OC 284:2) cites first the opinion of Tosfos and then the opinion of the Rosh, and concludes that "the common practice is like the first opinion," that is, not to mention Rosh Chodesh at all in the blessing after the Haftarah.