Leviticus 21:1-4

1The Lord said to Moses, “Give the following instructions to the priests, the descendants of Aaron. “A priest must not make himself ceremonially unclean by touching the dead body of a relative.

2The only exceptions are his closest relatives—his mother or father, son or daughter, brother,

3or his virgin sister who depends on him because she has no husband.

4But a priest must not defile himself and make himself unclean for someone who is related to him only by marriage.