Leviticus 20:17, 19

“If a man marries his sister, the daughter of either his father or his mother, and they have sexual relations, it is a shameful disgrace. They must be publicly cut off from the community. Since the man has violated his sister, he will be punished for his sin.

“Do not have sexual relations with your aunt, whether your mother’s sister or your father’s sister. This would dishonor a close relative. Both parties are guilty and will be punished for their sin.