Leviticus 20:17-21
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 must be cut off before the eyes of their people. He has dishonored his sister and will be held responsible.
18 “‘If a man lies with a woman during her monthly period and has sexual relations with her, he has exposed the source of her flow, and she has also uncovered it. Both of them must 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 sleeps with his aunt, he has dishonored his uncle. They will be held responsible; they will die childless.
21 “‘If a man marries his brother’s wife, it is an act of impurity; he has dishonored his brother. They will be childless.