And no man takes this honor unto himself, but he that is called of God, as was Aaron.
All Commentaries on Hebrews 5:4 Go To Hebrews 5
The Apostolic Constitutions
AD 375
Neither do we permit the laity to perform any of the offices belonging to the priesthood; as, for instance, neither the sacrifice, nor baptism, nor the laying on of hands, nor the blessing, whether the smaller or the greater: for "no one taketh this honour to himself, but he that is called of God."