Leviticus 20:12

20:12 If a man has sexual intercourse with his daughter-in-law, both of them must be put to death. They have committed perversion; their blood guilt is on themselves.

Leviticus 20:14

20:14 If a man has sexual intercourse with both a woman and her mother, it is lewdness. Both he and they must be burned to death, so there is no lewdness in your midst.