Leviticus 20:12, 17

“If a man has sex with his daughter-in-law, both must be put to death. They have committed a perverse act and are guilty of a capital offense.

“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.