1) THE SOURCE FOR HOW TO LIGHT THE FLAME UPON THE MIZBE'ACH
QUESTION: The Gemara discusses the verses from which the requirement for the various Ma'arachos on the Mizbe'ach are derived, according to the different opinions (Rebbi Yehudah, Rebbi Yosi, and Rebbi Meir).
Rebbi Yosi maintains that in addition to the Ma'arachah Gedolah and the Ma'arachah for the Ketores, there was a third Ma'arachah of "Kiyum ha'Esh," which he derives from the verse, "veha'Esh Al ha'Mizbe'ach Tukad Bo" (Vayikra 6:5). Rebbi Yehudah, who maintains that there was no third Ma'arachah of "Kiyum ha'Esh," says that the verse instead teaches "Hatzasas Alyasa" -- when the fire of the Mizbe'ach is kindled, the splinters must be ignited on the top of the Mizbe'ach (and not brought from below). The verse, according to Rebbi Yehudah, does not refer to a new Ma'arachah, but to how to light the fire on the main Ma'arachah on the Mizbe'ach.
Rebbi Yosi, on the other hand, derives the law of "Hatzasas Alyasa" from a different source, the verse expounded by Rebbi Shimon, "v'Nasnu Bnei Aharon ha'Kohen Esh Al ha'Mizbe'ach" (Vayikra 1:7), which teaches that the fire must be kindled on the top of the Mizbe'ach.
RASHI asks that if this verse teaches "Hatzasas Alyasa," why does it mention that the Kohanim ("Bnei Aharon ha'Kohen") must do it? It is obvious that the fire must be kindled by Kohanim, because it must be done on top of the Mizbe'ach, and, as Rebbi Shimon argues in the Gemara, a non-Kohen is not allowed on the Mizbe'ach. Why, according to Rebbi Shimon, does the verse need to say that a Kohen must kindle the flame if the verse specifies that the kindling must be done atop the Mizbe'ach?
Rashi answers that if the verse would have made no mention of the Kohanim, one might have understood it to mean that a non-Kohen may light the fire at the base of the Mizbe'ach and throw it onto the Mizbe'ach. The verse therefore teaches that a Kohen must light it.
Rashi's answer is problematic. In the Gemara, Rebbi Shimon rejects the interpretation of Rebbi Yehudah, who says that the verse teaches that a Kohen must light the fire on top of the Mizbe'ach, because "there is no reason to think that a non-Kohen is permitted to approach the Mizbe'ach." Although Rebbi Yehudah responds that the verse teaches that a non-Kohen may not kindle with a bellows from below, Rebbi Shimon does not accept this argument. Now, however, Rebbi Shimon himself says the same thing! That is, although the verse already teaches that "Hatzasas Alyasa" must be done on top of the Mizbe'ach, Rebbi Shimon finds it necessary to bring an additional source to teach that a Kohen must perform "Hatzasas Alyasa," and that a non-Kohen may not throw the flame up to the top of the Mizbe'ach. Why is Rebbi Shimon bothered with Rebbi Yehudah's interpretation of the verse if he eventually interprets the verse the same way?
ANSWER: TOSFOS (DH v'Chi) answers that when Rebbi Shimon says that the fire must be lit by a Kohen on the Mizbe'ach (and not by a non-Kohen below and thrown up to the Mizbe'ach), he does not refer to the act of "Hatzasas Alyasa," the kindling of the burning splinters to make the fire strong. It is not possible to perform "Hatzasas Alyasa" anywhere except on top of the Mizbe'ach, unless one stands below the Mizbe'ach and uses a bellows to strengthen the flame above. Rebbi Shimon maintains that the use of a bellows from below is not an option and thus no verse is needed to exclude it.
However, one might have thought that since there is a Mitzvah to bring a flame to the Mizbe'ach (despite the fact that a heavenly flame always burns there), the initial act of bringing the flame to the Mizbe'ach may be done by a non-Kohen below and thrown onto the Mizbe'ach. That is why this verse, which discusses bringing the fire and not kindling the fire, must specify that the act must be done by a Kohen. Rebbi Shimon understands that although kindling a fire from below with a bellows is not a practical option, throwing a fire to the top of the Mizbe'ach is a practical option. (The RITVA gives a similar explanation.)

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