Exodus 29:7-9

7Then you shall take 1the anointing oil and pour it on his head, and anoint him. 8You shall also bring his sons and put 2tunics on them. 9And you shall wrap their waists with 3sashes, Aaron and his sons, and fit 4caps on them, and they shall have 5the priesthood by a permanent statute. So you shall 67ordain Aaron and his sons.