Why did the Kohen Gadol wear linen Begadim when entering the Kodesh Kodashim on Yom Kipur, and not the eight regular Bigdei Kohen Gadol?
Rashi: Because they contained gold (which was used to make the Egel), and based on the principle 'Ein Kateigor Na'aseh Saneigor' (a prosecutor cannot become a defense counsel), it was not appropriate for him to enter the inner sanctum wearing gold.
Targum Yonasan: So that the gold should not recall the sin of the Golden Calf.
Why does the Pasuk insert the word "Kodesh"?
Rashi and Ramban (citing Toras Kohanim): To teach us that the Begadim currently under discussion are purchased from Hekdesh (from the funds of Bedek ha'Bayis, and that Aharon did not need to pay for them out of his own pocket). 1
Seforno: Because the angels appeared to the Nevi'im clothed in the same four linen garments. 2
Why does the Torah repeat "Bigdei Kodesh heim"?
Ramban #1 (citing Toras Kohanim): to teach us that the same applies to all the Bigdei Kehunah - both those of a Kohen Hedyot and those of the Kohen Gadol.
Ramban #2: To teach us that these Begadim are holy, just as the eight Begadim that the Kohen Gadol wears all the year round are holy. 1
Why does it say "Yilbash", "Yachgor and "Yitznof"?
Ramban (from Toras Kohanim): To teach 1 us that, although the Kohen Gadol has to wear different Bigdei Lavan in the afternoon than those that he wore in the morning 2 in the event that none are available, he may wear the same Begadim that he wore in the morning.
What is the meaning of "Yitznof"?
Rashi and Targum Onkelos: It means place on his head. 1
Ramban: It means to wind round his head. 2
How often does the Kohen Gadol have to immerse and Kidush of (washing) his hands and feet on Yom Kipur?
Rashi: Five 1 times - each time he changes from Avodas Chutz to Avodas P'nim 2 and each time he changes from Avodas P'nim to Avodas Chutz. And each change of garments requires Kidush two times (Yoma 31b). 3
Moshav Zekenim (18): These correspond to the five Avodos and five Tefilos of the day
Twice each, plus the first Tevilah early in the morning, when he begins the Avodah.
Moshav Zekenim (18): The 10 Kidushim correspond to the 10 times he says Hashem's Mefurash name (three in each of the three Viduyim, and he says "Chatas la'Shem" after the lottery.
Rashi writes that the Kohen Gadol did not wear gold in the Kodesh Kodashim, for 'Ein Kateigor Na'aseh Saneigor.' The gold Mizbe'ach was in the Heichal (and it is essential for Avodas Yom Kipur)! A calf was brought for the Milu'im, to atone for Chet ha'Egel, and also Par Yom Kipur does!
Moshav Zekenim: The inner Mizbe'ach was not only for Kaparah, the way Bigdei Kehunah and Yom Kipur atone. Also, there is more concern for the Kohen Gadol, similar to Aharon. 1 A Korban on the Mizbe'ach surely atones, just like a Chatas atones for Chet.
Why did he need to say this? A Kohen Hedyot never wears gold; all Kohanim may offer Ketores on the gold Mizbe'ach! (PF)
Rashi writes that the Kohen Gadol did not wear gold in the Kodesh Kodashim, for 'Ein Kateigor Na'aseh Saneigor.' He wears gold when offering the Temidim of Yom Kipur, and he uses gold Kelim, e.g. the incense pan and spoons!
Moshav Zekenim: Bigdei Kehunah atone. The other Kelim do not atone. Since the Tamid is brought with gold garments the entire year 1 , also now we are not concerned.
The Kohen Gadol is allowed to serve whenever he wants; only on Yom Kipur he must serve. The daily lotteries imply that normally, Hedyotim offered the Tamid! (PF)
Why does it say "Bad" (linen) four times?
Hadar Zekenim (citing Toras Kohanim): This excludes four garments (the Choshen, Efod, Me'il and Tzitz, which contain gold).