Gemara

(R. Yochanan): If Shelamim was slaughtered in the Heichal, it is Kosher;

It says "u'Shchato Pesach Ohel Mo'ed" - the Tefel should not be greater than the Ikar!

Question (Beraisa - R. Yehudah ben Beseira) Question: If Nochrim surrounded (and were shooting projectiles into) the Azarah, what is the source to permit Kohanim to enter the Heichal to eat Kodshei Kodoshim (in safety)?

Answer: "B'Kodesh ha'Kodoshim Tochalenu"

Summation of question: Why is this verse needed? It says "ba'Chatzer Ohel Mo'ed Yochluha" - the Tefel (the Azarah) should not be greater than the Ikar (the Heichal)!

Answer: A slave serves in front of his master. Therefore, it is even more proper to slaughter in a more Kadosh place;

A slave does not eat in front of his master. Therefore, it is less proper to eat in a more Kadosh place. 'Tefel should not be greater than Ikar' does not apply.

Zevachim 55a (Mishnah): Shelamim may be slaughtered anywhere in the Azarah.

(Beraisa): Regarding Shelamim it says "u'Shchato Pesach Ohel Mo'ed", and two more verses say "v'Shachat Oso Lifnei Ohel Mo'ed." These permit the other three directions for slaughtering Kodshim Kalim. A Kal va'Chomer permits Tzafon:

Kodshei Kodoshim are permitted in Tzafon, but not in other directions. Kodshim Kalim are permitted in other directions. All the more so in Tzafon is permitted!

R. Eliezer says, the verse permits slaughtering in Tzafon. A Kal va'Chomer would have forbidden this;

All the other directions are permitted for Kodshim Kalim, but not for Kodshei Kodoshim. Only one direction (Tzafon) is permitted for Kodshei Kodoshim, all the more so it is not permitted for other Kodshim (i.e. Kalim)! Therefore, "Ohel Mo'ed" permits Tzafon.

The first Tana uses one verse for the simple meaning, that the gate of the Heichal must be open (at the time of Shechitah). One verse permits Tzedadim (the sides) of the Heichal, and one forbids Tzidei Tzedadim. Tzafon doesn't need a verse;

R. Eliezer uses one verse to teach that the gate must be open. One verse permits Tzafon, and one permits the sides. He holds that obviously Tzidei Tzedadim are forbidden. No verse is needed for them.

(Rav Yehudah): If Shelamim was slaughtered before the gate of the Heichal was opened, it is Pasul. It says "u'Shchato Pesach Ohel Mo'ed", i.e. when it is open, but not when it is locked.

(Beraisa - R. Yosi b'Rebbi Yehudah): There were two Pishpeshim (small openings) in Beis ha'Chalifos (extensions of the Ulam to the sides), to permit the entire Azarah for eating Kodshei Kodoshim and Shechitas Kodshim Kalim.

Question: What permits in back of the Kodesh ha'Kodoshim? (From there, one could not see the openings, due to the wall in back of the Kodesh ha'Kodoshim.)

Answer (Rami bar Rav Yehudah): There was a Lul (window) in back of the Kodesh ha'Kodoshim to permit the entire Azarah for eating Kodshei Kodoshim and Shechitas Kodshim Kalim.

107b (Ula): One who slaughters Kodshim on the roof of the Heichal is liable, since no Korban may be slaughtered there.

Pesachim 85b (Rav): The roofs and Aliyos (upper stories) did not receive Kedushas Yerushalayim.

Question (Beraisa - Aba Sha'ul): The Aliyah above the Kodesh ha'Kodoshim was more Kodesh than the Kodesh ha'Kodoshim.

Answer (Rav Yosef): The Heichal is different, for it says "...Tavnis ha'Ulam...v'Aliyosav" and "Ha'Kol bi'Chsav mi'Yad Hash-m Alai Hiskil."

Rishonim

Rambam (Hilchos Ma'aseh ha'Korbanos 5:4): We may slaughter Kodshim Kalim anywhere in the Azarah, even in back of the Heichal. It says about Shelamim "u'Shchato Pesach Ohel Mo'ed" to permit all directions, for it did not specify a direction.

Kesef Mishneh: Rashi (55a DH Lehacshir) says that "Lifnei" connotes everything in front of the Heichal One verse is Machshir the sides, i.e. the entire width of the Azarah, lest we say that only what is opposite the opening is Kosher. Therefore, it says again "Lifnei", and did not repeat "Pesach". "Lifnei" includes all the air (i.e. width), for it does not say "opposite". One verse disqualifies Tzidei Tzedadim, e.g. chambers. Even if the content is Kodesh, they are Pasul for Shechitah. We do not say that since "Pesach" is not precise (it need not face the opening), also "Lifnei" is not precise. The Rambam says that "u'Shchato Pesach Ohel Mo'ed" permits all directions. This is a printing mistake. This verse teaches only that it must be "Pesach Ohel Mo'ed" (facing the opening of the Heichal, when it is open)! Rather, it should say "v'Shochat Oso Lifnei Ohel Mo'ed." What is the Rambam's source to permit in back of the Heichal?

Tosfos Yom Tov (Zevachim 5:7): The Kesef Mishneh overlooked Zevachim 55b, which explicitly says that a window permitted in back of the Heichal.

Minchas Chinuch (141 DH u'Mah): In Hilchos Beis ha'Bechirah, the Rambam did not mention that there was a window in back of the Kodesh ha'Kodoshim! The Kal va'Chomer that permits Shechitah in the Heichal applies also to the Kodesh ha'Kodoshim. See Tosfos 55b DH Shnayim (who says that the window in back did not allow seeing Pesach Ohel Mo'ed. In only allowed to see into the Kodesh ha'Kodoshim, and this sufficed to permit Shechitah.)

Aruch ha'Shulchan ha'Asid (71:16): The entire Azarah is Kosher for Shechitah, including the Heichal. The Kal va'Chomer includes also the Kodesh ha'Kodoshim, but he is liable for entering.

Rashi (Zevachim 55b DH v'Chad Lifsol): 'Tzidei Tzedadim' refers to chambers around the Azarah. Even if their inside would be Kodesh, one may not slaughter Kodshim there.

Shitah Mekubetzes (55b 1, citing Tosfos): In any case, the chambers did not have Kedushas Azarah! Rather, Tzidei Tzedadim refers to (north and south of the Heichal) past the corner of the Heichal. It teaches that if there were no Pishpeshim, it would be forbidden to slaughter there.

Likutei Halachos (Zevachim 55, Zevach Todah 33b DH v'Chad): Shitah Mekubetzes could have said that it forbids Shechitah when the Pishpeshim are closed. We can answer for Rashi that the verse disqualifies chambers even if they were built in the Azarah and open to the Azarah. They have full Kedushas Azarah, and a Tamei is Chayav Kares for going there, but one may slaughter there only if they are open to an opening of the Heichal. This is why Rashi said 'even if their inside would be Kodesh', and not 'even though their inside was Kodesh.' The Rambam holds like Rashi. This is why he did not teach about Tzidei Tzedadim, for he already taught about the chambers. However, the Rambam permits even in back of the Heichal. This connotes that all the more so, the sides are permitted, even though it is not Lifnei Ohel Mo'ed. He must rule like R. Yosi b'Rebbi Yehudah, who says that there were Pishpeshim in the Ulam. He must hold that Kedushas Ulam is like Kedushas Heichal. We hold that Kedushas Ulam is not like Kedushas Heichal! This is why even though the Ulam's opening had no door and it was always open, a Shelamim slaughtered before the Heichal's opening was open is Pasul. Rav Yehudah and many Amora'im say so. The Stam Mishnah and the Gemara on 56a connotes that the entire Azarah is Kosher for Shechitah (even though north and south of the Heichal faces only Pishpeshim of the Ulam, like R. Yosi b'Rebbi Yehudah)! Perhaps one can explain 'the entire Azarah', i.e. even south of the Mizbe'ach, is Kosher. This requires investigation. Perhaps the Rambam holds that the Pishpeshim were in the place of Chalifos, but the openings were in the Heichal wall. Rashi (Gitin 54b DH Hachi) says so, but here (55b DH Shnei) he retracted and said that they were in the wall of the Ulam, like the Tosefta says.When the Gemara asked about the sides, it answered 'he brings them to the corner', i.e. 'he brings the Korbanos to the corner of the Ulam on the side of the Heichal.

Rambam (ibid.): If it was slaughtered in the Heichal it is Kosher.

Minchas Chinuch (184 DH v'Ayen): The Gemara permitted entering the Heichal in pressed circumstances to eat Kodshim. Regarding Kodshim, it said that the Shechitah is Kosher. It seems that there is no Heter to enter to slaughter, for this is not Avodah, and one who does so is liable for entering without need, just the Shechitah is Kosher.

Rambam (ibid.): If it was slaughtered on the roof of the Heichal it is Pasul, for the roofs are not Kosher for Shechitah at all. Only the floor of the Azarah is Kosher.

Rashi (Pesachim 86a DH Ta): When the Gemara asked from a Beraisa that says that the roof of the Heichal is Kodesh, we could not say that the Heichal is different due to the verse, for the verse does not mention the roof. (It discusses only Aliyos.)

Kesef Mishneh: Rav Yosef answered that the Aliyos of the Heichal were Kodesh, and this connotes that also the roofs were. Really, the Aliyos were different, due to the verse. The verse did not mention the roof, so Rav's rule (that the roofs were not Kodesh) applies to it. The Rambam says 'only the floor' to exclude Aliyos. I later found that Zevachim 107b explicitly says that no Korban may be slaughtered on the roof of the Heichal.

Maharsham (5:1 DH v'Hinei): The Beis Yosef (Sof Siman 15brings the Mordechai and Maharik, who were unsure whether Kedushas Beis ha'Keneses is like the Heichal or like the Azarah. An Aliyah of a Beis ha'Keneses is Kodesh only if the Kedushah is like the Heichal. However, the roof even of the Heichal was not Kodesh, so in any case the roof of the Beis ha'Keneses is not Kodesh.