Leviticus 18:17-19

Living Bible

¹⁷ You may not marry both a woman and her daughter or granddaughter, for they are near relatives, and to do so is horrible wickedness. ¹⁸ You shall not marry two sisters, for they will be rivals. However, if your wife dies, then it is all right to marry her sister.

¹⁹ “There must be no sexual relationship with a woman who is menstruating;