What is the ruling on a husband leaving the marital home to live with a foreign Christian woman, cutting off support and his ties with his family, and requesting a divorce? And is it permissible for the wife to try to get him back?

Among the gravest sins is for a man to neglect his wife and children, for the Prophet, peace and blessings be upon him, said: "It is sufficient sin for a man to neglect those whom he supports," and he also said: "Each of you is a shepherd, and each of you is responsible for his flock." Therefore, he must be advised and warned of Allah's punishment. If he marries another woman, he is obligated to be just. If he is committing haram (definition) acts, he must fear Allah. If he insists on neglecting them, and the wife fears harm, then there is no blame upon her if she seeks divorce (talaq (definition)) or annulment (khul'), and refers the matter to a judge. It is preferable to try to advise him and strive for his return, and to involve someone who holds influence with him; for divorce is the last resort.