Leviticus 16:33-34

Evangelical Heritage Version

³³ He shall make atonement for the Most Holy Place, and he shall make atonement for the Tent of Meeting and for the altar. He shall make atonement on behalf of the priests and all the people of the assembly. ³⁴ This shall be a permanent regulation for you to make atonement for the people of Israel from all their sins once a year.

So Aaron did as the Lord had commanded Moses.