Adam Clarke's Commentary on the Bible - Leviticus 16:4
He shall put on the holy linen coat - He was not to dress in his pontifical garments, but in the simple sacerdotal vestments, or those of the Levites, because it was a day of humiliation; and as he was to offer sacrifices for his own sins, it was necessary that he should appear in habits suited to the occasion. Hence he has neither the robe, the ephod, the breastplate, the mitre, etc.; these constituted his dress of dignity as the high priest of God, ministering for others and the... read more
Adam Clarke's Commentary on the Bible - Leviticus 16:3
With a young bullock for a sin-offering - The bullock was presented as a sin-offering for himself, his family, the whole priesthood, and probably the Levites. The ram was for a burnt-offering, to signify that he and his associates were wholly consecrated, and to be wholly employed in this work of the ministry. The ceremonies with which these two sacrifices were accompanied are detailed in the following verses. read more