Exodus 29:8-11

8Present his sons as well and clothe them with tunics. 9Wrap the sashes around Aaron and his sons and tie headbands on them. The priesthood shall be theirs by a permanent statute. In this way you are to ordain Aaron and his sons.

10You are to present the bull at the front of the Tent of Meeting, and Aaron and his sons are to lay their hands on its head. 11And you shall slaughter the bull before the LORD at the entrance to the Tent of Meeting.