Is the wife sinful if she requests a divorce from her husband or from his second wife, with whom he had a relationship before marriage, and is it permissible for the husband to be married to both of them at the same time?

Accusing a chaste woman of adultery is a grave sin. It is permissible to marry an adulteress if she repents and her womb is cleared, but some scholars hold that it is not permissible to marry her before repentance. It is not permissible for a woman to seek divorce from her husband without cause; in such a case, the scent of Paradise will be forbidden to her. Nor is it permissible for her to seek the divorce of her sister [in faith] so that she may have [her husband] to herself. If the request for divorce is based on sound advice due to a legitimate reason, there is no objection to it. It is not permissible for a husband to house two wives in the same dwelling without their consent, but it is permissible for him to have them both under his marital bond.