Exodus 29:9-11

Put the headbands on their heads, and tie cloth belts around their waists. Aaron and his descendants will be priests in Israel, according to a rule that will continue from now on. This is how you will appoint Aaron and his sons as priests. “Bring the bull to the front of the Meeting Tent, and Aaron and his sons must put their hands on the bull’s head. Then kill the bull before the LORD at the entrance to the Meeting Tent.