Exodus 29:8-11

8You must also bring his sons and clothe them with tunics.

9Tie the sashes on Aaron and his sons and fasten headbands on them. The priesthood is to be theirs by a permanent statute. This is the way you will ordain Aaron and his sons.

10“You are to bring the bull to the front of the tent of meeting, and Aaron and his sons must lay their hands on the bull’s head.

11Slaughter the bull before the Lord at the entrance to the tent of meeting.