Why does the Torah switch from "Aharon" to "ha'Kohen asher Yimshach oso ... "?
Rashi and Rashbam: Since throughout the Parshah, the Torah referred exclusively to Aharon, the Torah found it necessary to explain that the same applies to the Kohanim Gedolim who serve after him. 1
Kol Eliyahu and Divrei Eliyahu: Vayikra Rabah (21:7) states that Aharon was permitted to enter the Kodesh ha'Kodashim on any day 2 , with the Korbanos mentioned here. Until now, the Torah discussed this. Now it teaches us that every Yom Kipur, the Kohen Gadol has a Mitzvah to enter with these Korbanos.
Yerushalmi Horayos, 3:2: To incorporate a Kohen Gadol who is not the son of the previous Kohen Gadol in the Avodas ha'Yom of Yom Kipur. 3
What is "va'Asher Yemalei es Yado ? " coming to teach us"?
Rashi and Seforno: It incorporates a Kohen Gadol who is initiated by wearing the eight Begadim, and who was not anointed with Shemen ha'Mishchah - in the Avodas ha'Yom on Yom Kipur. 1
During the era of the second Beis-ha'Mikdash, when the Shemen ha'Mishchah was not available.
What are the connotations of "Lechahein Tachas Aviv"?
Rashi: It teaches us that if the Kohen Gadol's son is worthy to succeed his father, 1 he has priority over all other contenders. 2
Sifra: It implies that the Kohen Gadol's son only succeeds his father.
Moshav Zekenim: Similarly, the head of Kalah (a gathering to learn the Dinim of Yom-Tov before each Yom-Tov), if his son is worthy to succeed him, he has priority.
Refer to 16:32:3.1:1.
What are the implications of "va'Asher Yemalei Es Yado"??
Sifra: It implies that the Kohen Gadol's son succeeds his father - provided he is worthy of the title. 1
See Torah Temimah, note 141.
Why does the Torah not write simply 'Ve'chiper ha'Kohen Asher Yechahen Tachas Aviv' (See Torah Temimah, note 139)?
Yoma, 5a: To teach us that, in spite of the fact that a Gadol Gadol is inducted by being anointed and by wearing the eight Bigdei Kehunah for seven consecutive days, if Bedieved he was anointed or wore the eight Bigdei Kehunah for only one day, his induction is valid. 1
See Torah Temimah, note 140.
Why does the Torah need to add the (otherwise superfluous) words "Velavash es Bigdei ha'Bad Bigdei ha'Kodesh"?