Leviticus 21:1-5

1Then the LORD said to Moses, “Speak to Aaron’s sons, the priests, and tell them that a priest is not to defile himself for a dead person among his people, 2except for his immediate family—his mother, father, son, daughter, or brother, 3or his unmarried sister who is near to him, since she has no husband. 4He is not to defile himself for those related to him by marriage, and so profane himself.

5Priests must not make bald spots on their heads, shave off the edges of their beards, or make cuts in their bodies.