Leviticus 20:17-19

New Catholic Bible

¹⁷ If a man marries his sister, his father’s daughter or his mother’s daughter, and he sees her nakedness and she sees his nakedness, it is shameful. They shall be cut off from their people, for he uncovered his sister’s nakedness and he shall bear his guilt.^[a]

¹⁸ “ ‘If a man has sex with a woman during her menstrual time, they shall have uncovered her flow of blood, and they shall both be cut off from among their people. ¹⁹ You shall not uncover the nakedness of your mother’s sister or your father’s sister, for someone who uncovers a close relation shall bear his guilt.