The high priest because he has been dedicated by the anointing oil of his God

 Leviticus 21:1-24

The high priest, the one among his brothers who has had the anointing oil poured on his head and who has been ordained to wear the priestly garments, must not let his hair become unkempt or tear his clothes. He must not enter a place where there is a dead body. He must not make himself unclean, even for his father or mother, nor leave the sanctuary of his God or desecrate it, because he has been dedicated by the anointing oil of his God. I am the Lord.

The Lord said to Moses,  “Say to Aaron: ‘For the generations to come none of your descendants who has a defect may come near to offer the food of his God.

He may eat the most holy food of his God, as well as the holy food; yet because of his defect, he must not go near the curtain or approach the altar, and so desecrate my sanctuary. I am the Lord, who makes them holy.

Because of their position and duties, the priests are subject to particularly stringent regulations on ritual purity. Anything which makes them 'unclean' means they may not touch anything in God's holy sanctuary. The rules for the high priest are even stricter compare 11 with 102; 13014 with 7. No one with any physical defect may serve as priest, though he may eat the holy bread.

Why?

For the priests are God's servants, and they are the chosen one who has to be Holy to serve the Lord.

Priest life and marriage and behavior have to away from unclean.

祭司家中死人與婚姻的規定，其他都不可沾染自己。

祭司可以娶寡婦不可娶被休的婦人。大祭司更嚴格。拿細耳人的要求與大祭司ㄧ樣。只要我們是祭司就有此職份。

身體不便的利未人可以享受祭司的權利·但是無需服事，是神的恩典。

大祭司服事時代表以色列人所以必須犧牲自己。

How?

Be holy to be a Christian. For God is Holy!