and he said to Aaron, “Take a bull calf as a sin offering and a ram as a burnt offering, [each] without blemish, and offer both before the Lord.

Then say to the Israelites, ‘Take a male goat as a sin offering, and a calf and a lamb, both one year old, without blemish, as a burnt offering,

So Aaron approached the altar and killed the calf as the sin offering, which was designated for himself.