Leviticus 18:15-18

¹⁵Do not sleep with your daughter-in-law. She is your son's wife; do not sleep with her.

¹⁶Do not sleep with your brother's wife; do not dishonor him in this way.

¹⁷Do not sleep with a woman and her daughter, or with her son's daughter or her daughter's daughter. They are close relatives to her, and sleeping with them would be wicked.

¹⁸You must not marry your wife's sister as a second wife and sleep with her while your first wife is alive.