Leviticus 21:2-4

The Voice

² There is an exception: a priest is allowed to touch the dead body of his closest family members—his mother, father, son, daughter, brother, ³ and any sister who is still a virgin when she dies. Since she has no husband, the priest is her closest relative, so he is allowed to make himself impure for her. ⁴ A priest must not render himself impure and defile himself by touching the corpse of a person related to him only by marriage.