What is the ruling of the Sharia on a man who committed adultery with a married woman, then married her daughter, and continued to commit adultery with the mother after the marriage, and fathered children with her daughter, then divorced her? Is it permissible for him to return to his wife after some sheikhs issued a fatwa prohibiting her to him due to his sexual relations with both the mother and the daughter?

A man has committed a grave sin by engaging in incestuous fornication (zina with a mahram (definition)). It is obligatory for him to repent and stay away from the causes that might lead him to commit it again. Scholars have differed regarding the ruling on his returning to his wife, whose mother he fornicated with. The Hanafis and Hanbalis hold that unlawful intercourse renders lawful that which was previously lawful (al-wat' al-haram (definition) yuharrim al-halal (definition)), thus it is not permissible for him to take her back. The Malikis and Shafi'is, however, hold that unlawful intercourse does not render lawful that which was previously lawful (al-wat' al-haram la yuharrim al-halal), and it is permissible for him to marry the daughter of the woman with whom he fornicated. This is the more preponderant view, because Allah has forbidden the daughter of the wife, not the daughter of the woman with whom one has fornicated, and the woman with whom one has fornicated is not a wife.