Or HaChaim on Leviticus 16:3/אור החיים על ויקרא ט״ז:ג׳

1 בזאת יבא אהרון, "Aaron is to enter with the following:" The reason the Torah repeats Aaron's name though it could have written merely: "with this he is to enter, etc.," is that what has been written in verse 2 applied only to Aaron. From this verse on the Torah deals with commandments applicable not only to the High Priest personally; seeing that Aaron's duties in the Sanctuary were performed on behalf of the entire people, and the clothing he wore while performing this service was as a representative of the people as a whole, G'd commanded His people to perform these rites using Aaron as their representative so as to obtain forgiveness once a year. Torat Kohanim emphasises that the linen tunic Aaron wore was paid for by the Temple treasury. The Torah hinted at this by mentioning Aaron by name as the people's representative.