What is the Pasuk referring to when it writes "Ach el ha'Paroches Lo Yavo" and "ve'el ha'Mizbe'ach Lo Yigash"?
Rashi: It is referring to the seven sprinklings that take place on Yom Kipur and approaching the Mizbe'ach ha'Olah 1 to bring Korbanos, respectively.
See Sifsei Chachamim.
Why does the Pasuk need to mention both the Paroches and the Mizbe'ach?
Rashi and Da'as Zekenim, citing the Sifra: Because on the one hand, the Paroches is inside the Heichal - and the Mizbe'ach is not, and on the other, the Mizbe'ach is designated for the Avodah - and the Paroches is not.
What is "Ach" coming to preclude?
Ba'al ha'Turim (citing the Sifra) 1 : It precludes from the prihibition where there are no Kohanim, in which case Levi'im may enter; if there are no Tehorim, in which case Teme'im may enter and if there are no Teme'im, Ba'alei-Mumim may ente'. 2
B'choros, 43b: It precludes entering between the Ulam and the Mizbe'ach in order to beat plates to overlay the Mizbe'ach, which is pemitted. 3
What are the connotations of "ve'Lo Yechalel Es Mikdashai"?
Rashi #1: It means that if a Ba'al Mum served in the Beis Hamikdash, his Avodah is Pasul. 1
Rashi #2 (on 20:3): It means that if a Ba'al-Mum served in the Beis-Hamikdash, he defiles the Kedushah of K'nesses Yisrael, who are sanctified to Hashem.
This refers specifically to real blemishes, but not to those that are Asur only because of Mar'is Ayin. See Torah Temimah, note 159.
Rashi learns from "ve'Lo Yechalel" that if a Ba'al Mum served, his Avodah is Pasul. Kidushin 66b learns this from "es Berisi Shalom" (Bamidbar 25:13) - when he is Shalem, and not lacking!
Moshav Zekenim: The Pasuk here implies that if he served b'Mezid, it is Pasul. "Brisi Shalom" teaches that even b'Shogeg, it is Pasul.
Keren Orah (Ta'anis 17a): "Barech Hashem Cheilo" (Devarim 33:11) teaches that if we find that a Kohen was a Chalal, be'Di'eved his Avodah is Kosher (Pesachim 72b). One might have thought that the same applies to a Ba'al Mum; the extra Pasuk teaches that this is not so.
Rashi learns from "ve'Lo Yechalel" that if a Ba'al Mum served, his Avodah is Pasul. This is like R. Chanina ben Gamliel, who extrapolates the positive from the negative. What is the source for R. Meir, who does not?
Shevu'os 36b: For Isur, R. Meir agrees that from the negative you infer the positive. 1
He learns from "es Brisi Shalom" (Bamidbar 25:13) - when he is Shalem, and not lacking. 2 (PF)
Why did the Moshav Zekenim, citing R. Yehudah ha'Chasid, leave this difficult? The Rishonim cite different texts in Shevu'os 36b. Perhaps in his text, R. Meir extrapolates the positive from the negative only for a severe Isur; Chachamim hold that there is no Misah for a Ba'al Mum who served (Tosefta Zevachim 12:17. - PF)
Some say that two Pasuks are needed (refer to 21:23:151:1,2), but Da'as Zekenim (17) and Hadar Zekenim (15) asked, and did not answer, why one Pasuk does not suffice! (PF)
