Leviticus 20:17; Leviticus 20:20

17 "If a man takes his sister, a daughter of his father or a daughter of his mother, and sees her nakedness, and she sees his nakedness, it is a disgrace, and they shall be cut off in the sight of the children of their people. He has uncovered his sister's nakedness, and he shall bear his iniquity.

20 If a man lies with his uncle's wife, he has uncovered his uncle's nakedness; they shall bear their sin; they shall die childless.