Exodus 29:6-9

And you shall set the turban on his head and put the holy crown on the turban. You shall take the anointing oil and pour it on his head and anoint him. Then you shall bring his sons and put coats on them, and you shall gird Aaron and his sons with sashes and bind caps on them. And the priesthood shall be theirs by a statute forever. Thus you shall ordain Aaron and his sons.