Leviticus 21:1-6

GOD spoke to Moses: “Speak to the priests, the sons of Aaron. Tell them, A priest must not ritually contaminate himself by touching the dead, except for close relatives: mother, father, son, daughter, brother, or an unmarried sister who is dependent on him since she has no husband; for these he may make himself ritually unclean, but he must not contaminate himself with the dead who are only related to him by marriage and thus profane himself. “Priests must not shave their heads or trim their beards or gash their bodies. They must be holy to their God and must not profane the name of their God. Because their job is to present the gifts of GOD, the food of their God, they are to be holy.