Leviticus 16:33-34

New Century Version

³³ and make the Most Holy Place, the Meeting Tent, and the altar ready for service to the Lord. He must also remove the sins of the priests and all the people of Israel so they will belong to the Lord. ³⁴ That law for removing the sins of the Israelites so they will belong to the Lord will continue forever. You will do these things once a year.”

So they did the things the Lord had commanded Moses.