Exodus 29:9-11

You shall gird them with sashes, Aaron and his sons, and bind caps on them, and they shall have the priesthood by a perpetual statute. So you shall ordain Aaron and his sons. “Then you shall bring the bull before the tent of meeting, and Aaron and his sons shall lay their hands on the head of the bull. You shall slaughter the bull before the LORD at the doorway of the tent of meeting.