Leviticus 21:2-4

New Century Version

² But if the dead person was one of his close relatives, he may touch him. The priest may make himself unclean if the dead person is his mother or father, son or daughter, brother or ³ unmarried sister who is close to him because she has no husband. The priest may make himself unclean for her if she dies. ⁴ But a priest must not make himself unclean if the dead person was only related to him by marriage.