Leviticus 20:17-21

17‘If a man takes his sister, his father’s daughter or his mother’s daughter, so that he sees her nakedness and she sees his nakedness, it is a disgrace; and they shall be cut off in the sight of the sons of their people. He has uncovered his sister’s nakedness; he bears [responsibility for] his guilt.

18If a man lies [intimately] with a woman during her menstrual cycle and uncovers her nakedness, he has exposed her flow, and she has uncovered the flow of her blood; both of them shall be cut off from their people [excluding them from the atonement made for them].

19You shall not uncover the nakedness of (have intimate relations with) your mother’s sister or your father’s sister, for such a one has uncovered his blood relative; they will bear their guilt.

20If there is a man who lies [intimately] with his uncle’s wife, he has uncovered his uncle’s nakedness; they will bear their sin. They will die childless.

21If a man takes his brother’s wife, it is a hated and unclean thing; he has uncovered his brother’s nakedness. They will be childless.