Leviticus 18:17-19

Amplified Bible

¹⁷ You shall not uncover the nakedness of a woman and her daughter, nor shall you take her son’s daughter or her daughter’s daughter to uncover their nakedness (have intimate relations with them); they are [her] blood relatives; it is an outrageous offense. ¹⁸ You shall not marry a woman in addition to her sister as a rival while she is alive, to uncover her nakedness.

¹⁹ ‘Also you shall not approach a woman to uncover her nakedness during her menstrual impurity and ceremonial uncleanness.