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, and, in light of his participation in the Golden Calf, 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 remind Hashem of 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
Having written "Yilbash", "Yachgor and "Yitznof", why does the Torah see fit to add "u'Leveisham" (Malbim)?
Ramban: To teach us that, although the Kohen Gadol has to wear different Begadim for the Tamid shel bein ha'Arbayim than those that he wore for the Tamid shel Shachar, 1 in the event that none are available, he may wear the same Begadim that he wore in the morning.
See Mishnah Yoma, 3:7.
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 Tovel on Yom Kipur?