John Calvin Commentary Leviticus 9:7

"And Moses said unto Aaron, Draw near unto the altar, and offer thy sin-offering, and thy burnt-offering, and make atonement for thyself, and for the people; and offer the oblation of the people, and make atonement for them; as Jehovah commanded." — Leviticus 9:7 (ASV)

And Moses said unto Aaron, Go unto the altar. Here is repeated what was stated elsewhere: that the priest, being himself a sinner, must first entreat for himself before he propitiates God towards others. Hence the Apostle justly infers that the legal priesthood was weak and merely typical (Hebrews 5:1).

For none can be a true peacemaker, except one who, in reliance on his perfect innocence, presents himself before God to obtain pardon for others and, being pure from every blemish, requires no expiation for himself. All else to the end of the chapter I pass over, because Moses only records how Aaron sacrificed according to God’s command and the legal ritual.