Leviticus 21:1-5New Revised Standard Version (NRSV)
The Holiness of Priests
21 The Lord said to Moses: Speak to the priests, the sons of Aaron, and say to them:
No one shall defile himself for a dead person among his relatives, 2 except for his nearest kin: his mother, his father, his son, his daughter, his brother; 3 likewise, for a virgin sister, close to him because she has had no husband, he may defile himself for her. 4 But he shall not defile himself as a husband among his people and so profane himself. 5 They shall not make bald spots upon their heads, or shave off the edges of their beards, or make any gashes in their flesh.