Charles Ellicott Commentary Leviticus 9:2

"and he said unto Aaron, Take thee a calf of the herd for a sin-offering, and a ram for a burnt-offering, without blemish, and offer them before Jehovah." — Leviticus 9:2 (ASV)

A young calf for a sin offering. Literally, this means a calf, the son of a bull. According to the canonical law, this was a calf in its second year, while a steer (a son of a bull, translated in the Authorized Version as “young bullock”) was defined as three years old, or in its third year . Before they could mediate for the people's forgiveness, Aaron and his sons first had to bring a sin offering for themselves, probably in expiation for any feeling of pride they might have fostered from being so highly distinguished and chosen as the people's mediators.

This sin offering, however, showed him that, though a high priest, he was beset with the same infirmities and stood in need of the same atonement as the people he represented. Since this is the only instance where a calf is appointed for a sin offering, and since the offerer commanded to bring this exceptional sacrifice is Aaron, Jewish tradition maintains that it was designed to refer to the sin of the golden calf which he made for the people (Exodus 32:4–6). This interpretation is so old and universal that it is expressed in the ancient Chaldee Version of the Pentateuch. This understanding seems to find support in Leviticus 9:7.

Before the Lord. That is, before the door of the tent of meeting (Leviticus 1:11), on the altar of burnt offering.