Leviticus 21:1-6

And the LORD said to Moses, “Speak to the priests, the sons of Aaron, and say to them, No one shall make himself unclean for the dead among his people, except for his closest relatives, his mother, his father, his son, his daughter, his brother, or his virgin sister (who is near to him because she has had no husband; for her he may make himself unclean). He shall not make himself unclean as a husband among his people and so profane himself. They shall not make bald patches on their heads, nor shave off the edges of their beards, nor make any cuts on their body. They shall be holy to their God and not profane the name of their God. For they offer the LORD’s food offerings, the bread of their God; therefore they shall be holy.