Leviticus 21:1-6

The LORD said to Moses, “Speak to the priests, the sons of Aaron, and say to them: ‘A priest must not make himself ceremonially unclean for any of his people who die, except for a close relative, such as his mother or father, his son or daughter, his brother, or an unmarried sister who is dependent on him since she has no husband—for her he may make himself unclean. He must not make himself unclean for people related to him by marriage, and so defile himself. “ ‘Priests must not shave their heads or shave off the edges of their beards or cut their bodies. They must be holy to their God and must not profane the name of their God. Because they present the food offerings to the LORD, the food of their God, they are to be holy.