Bible: Lev. 20:17-18
20:17 “‘If a man has sexual intercourse with 1 his sister, whether the daughter of his father or his mother, so that he sees her nakedness and she sees his nakedness, it is a disgrace. They must be cut off in the sight of the children of their people. 2 He has exposed his sister’s nakedness; he will bear his punishment for iniquity. 3 20:18 If a man has sexual intercourse with a menstruating woman and uncovers her nakedness, he has laid bare her fountain of blood and she has exposed the fountain of her blood, so both of them 4 must be cut off from the midst of their people.