Is the marriage of a Muslim man to a woman of the People of the Book, with whom he had committed fornication and then contracted marriage, valid, knowing that she refrained from fornication after their repentance and before the marriage contract? Or must he divorce her and then remarry her? And what is the way to rectify this marriage in a manner that pleases Allah?

If a woman refrains from zina (fornication/adultery), repents, and resolves not to return to it, then she has repented, and the marriage contract with her is valid. However, merely refraining without repentance and resolve does not count as repentance. Marrying a Kitabiyyah (woman of the People of the Book) who is not chaste is impermissible according to most scholars. The contract is not rectified by divorce; rather, it is rectified by renewing it with the guardian's offer and the husband's acceptance, in the presence of two witnesses, along with striving to invite her to Islam.