It is well known that any illicit sexual relationship or any form of intimacy between two persons of the opposite sex is prohibited in Islam.
Allah commands us saying, (Nor come nigh to adultery: for it is a shameful (deed) and an evil, opening the road (to other evils).) (Al-Isra’ 17: 32)
Furthermore, both men and women are ordered to lower their gaze and to stay away from any act that might lead them to an illicit affair. Allah Almighty commands believing men and believing women alike to lower their gaze and to guard their sexual parts: (Tell the believing men that they should lower their gazes and guard their sexual organs; that is purer for them. Indeed, Allah is well-acquainted with what they do. And tell the believing women that they should lower their gazes and guard their sexual organs, and not display their adornment, except that which is apparent of it; and that they should draw their head-coverings over their bosoms, and not display their adornment….) (An-Nur 24: 30-31)

Sheikh Ahmad Kutty, a senior lecturer and Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states the following: Allah the Almighty orders us to remain faithful and stay away from adultery and fornication. By admitting to his illicit relationship and still continuing the same without remorse, your husband is guilty of a most heinous sin. If he persists in this behavior in spite of the advice from you and the imam, you have every right to seek a divorce. In fact, if the man is persistent in such behavior, Islamically you should seek a divorce. Allah says: (The good husbands for good wives and vile husbands for vile wives…) (An-Nur 24: 26). Based on this, a wife should separate from him in bed unless he has repented.