Leviticus 16:33-34

International Standard Version

³³ and make atonement for the sacred sanctuary, the Tent of Meeting, and the altar where atonement is carried out. He is also to make atonement for the priests and the people of the entire assembly. ³⁴ This will be a perpetual statute for you as you make atonement once a year for the Israelis on account of all their sins.”

So Moses did just as the Lord had commanded him.