Because of Marriage People Who Become Unlawful to Marry

9. A number of our people have narrated from Sahl ibn Ziyad from Musa ibn Ja’far from “Amr ibn Sa‘id from Musaddiq ibn Sadaqah from ‘Ammar who has said the following: “About the case of a man who has a slave-girl and his grandson falls on her (does sexual intercourse) before his grandfather or that a man commits fornication with a woman; if she is lawful for his father to marry, abu ‘Abd Allah عليه السلام, said, ‘No, it is not permissible. Only if the man marries her and goes to bed with her then his son commits fornication with her it does not harm him because unlawful does not make lawful ones unlawful and so also is the case of the slave-girl.’”