Is the husband entitled to withhold the remainder of the mahr and the deferred mahr from his wife if he discovers that she allowed her ex-husband into their home after the marriage contract, claiming that her ex-husband was eating with her and that she possessed a key to her home, despite the denial of both the wife and her ex-husband regarding the existence of a physical relationship?

If the wife has an emotional relationship with her ex-husband, she has disobeyed her Lord and fallen short in her duty to her husband. She must protect her husband in his absence, regarding herself and his property. She should be advised, and if she repents and her conduct becomes righteous, he should keep her and treat her well. Otherwise, divorce is better, especially if she has neglected the rights of Allah or is unchaste, as this diminishes the husband's religiosity and there is no guarantee that she will not corrupt his bed. The dowry is a right of the woman, and the husband is not entitled to withhold it from her merely for lying or allowing someone he dislikes into his home. However, if it is proven that she committed adultery by confession, then the husband may oppress her and restrict her so that she may ransom herself from him by forfeiting the remainder of the dowry. If he divorces her without ransom, she is entitled to the remainder of her dowry.