Leviticus 20:17-20

17“ ‘If a man marries his sister, the daughter of either his father or his mother, and they have sexual relations, it is a disgrace. They are to be publicly removed from their people. He has dishonored his sister and will be held responsible. 18“ ‘If a man has sexual relations with a woman during her monthly period, he has exposed the source of her flow, and she has also uncovered it. Both of them are to be cut off from their people. 19“ ‘Do not have sexual relations with the sister of either your mother or your father, for that would dishonor a close relative; both of you would be held responsible. 20“ ‘If a man has sexual relations with his aunt, he has dishonored his uncle. They will be held responsible; they will die childless.