What is the ruling on a Muslim remaining married to a Christian woman who rejects Islam and threatens to deprive him of his child?

Marriage to a Kitabiyyah (a woman from the People of the Book) is disliked due to the harms that result from it, including its impact on the children's beliefs and morals. A child follows the better of their two parents in religion.

If it is highly probable that the child will be raised upon the creed and morals of Islam, then that is good. However, if you fear the mother's influence on the child, then divorce her and strive to obtain custody. If it is highly probable that the mother will obtain custody, then keep her within your marital bond and be diligent in raising the child upon goodness. There is no sin in refraining from having children with her for fear of the children becoming disbelievers.

One should not despair of her embracing Islam, and should supplicate for her, and be keen on encouraging her towards Islam and demonstrating its virtues. We draw attention to the danger of residing in lands of disbelief, especially for children.