Leviticus 21:1-6

And the LORD said unto Moses, Speak unto the priests the sons of Aaron, and say unto them, There shall none be defiled for the dead among his people: but for his kin, that is near unto him, that is, for his mother, and for his father, and for his son, and for his daughter, and for his brother, and for his sister a virgin, that is nigh unto him, which hath had no husband; for her may he be defiled. But he shall not defile himself, being a chief man among his people, to profane himself. They shall not make baldness upon their head, neither shall they shave off the corner of their beard, nor make any cuttings in their flesh. They shall be holy unto their God, and not profane the name of their God: for the offerings of the LORD made by fire, and the bread of their God, they do offer: therefore they shall be holy.