Leviticus 21:1-4

1And the Lord said to Moses, “Speak to the priests, the sons of Aaron, and say to them: ‘None shall defile himself for the dead among his people,

2except for his relatives who are nearest to him: his mother, his father, his son, his daughter, and his brother;

3also his virgin sister who is near to him, who has had no husband, for her he may defile himself.

4Otherwise he shall not defile himself, being a chief man among his people, to profane himself.