Exodus 29:6-9

and you shall set the turban on his head and put the holy crown on the turban. Then you shall take the anointing oil and pour it on his head and anoint him. You shall bring his sons and put tunics on them. 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.