What is the ruling on a disbeliever marrying a disbeliever, such as a Christian man marrying a Christian woman, or a person who abandons prayer? And is such a marriage valid?

The marriages of disbelievers are valid, and they are upheld if they embrace Islam or seek our judgment, unless there is an impediment between the spouses that prevents the continuation of the marriage, such as prohibited degrees of relationship. As for one who abandons prayer, if his abandonment is due to laziness and not denial, then according to the majority of scholars, he is not considered a disbeliever, and his marriage is like the marriage of a Muslim transgressor.