Leviticus 21:8

Thou, O Moses, and whosoever shall succeed in thy place, to whom it belongs to see those and other of my laws observed, shall take care that the priest be holy, and do not defile himself by any of these forbidden marriages, though he would do it. He shall be holy unto thee; either

1. In thy esteem, and therefore shall not give thee cause to think meanly and irreverently of him by his defiling or debasing of himself with irregular mixtures. Or,

2. To thy use or service, in whose name he is to act with God, and therefore shall preserve himself in a state of holiness and acceptation with God. For I the Lord am holy, and therefore my ministers must be such also.