Leviticus 21:1-4

1The Lord said to Moses, “Speak to the priests, the sons of Aaron, and say to them: ‘A priest must not make himself ceremonially unclean for any of his people who die,

2except for a close relative, such as his mother or father, his son or daughter, his brother,

3or an unmarried sister who is dependent on him since she has no husband—for her he may make himself unclean.

4He must not make himself unclean for people related to him by marriage, and so defile himself.