Leviticus 18:11

18:11 You must not have sexual intercourse with the daughter of your father’s wife born of your father; she is your sister. You must not have intercourse with her.

Leviticus 20:19

20:19 You must not expose the nakedness of your mother’s sister and your father’s sister, for such a person has laid bare his own close relative. They must bear their punishment for iniquity.