Exodus 29:8-12

You shall also bring his sons and put tunics on them.

And you shall wrap their waists with sashes, Aaron and his sons, and fit caps on them, and they shall have the priesthood by a permanent statute. So you shall ordain Aaron and his sons. The Sacrifices

“Then you shall bring the bull in front of the tent of meeting, and Aaron and his sons shall lay their hands on the head of the bull.

And you shall slaughter the bull before the Lord at the doorway of the tent of meeting.

Then you shall take some of the blood of the bull and put it on the horns of the altar with your finger; and you shall pour out all the rest of the blood at the base of the altar.