What is the ruling on someone who says, "If I marry a woman and she does such-and-such, then each of us will go our separate ways, and we will not live together for another moment," when he is not yet married?

The correct view is that divorce is not valid before marriage. Therefore, the utterance made by the aforementioned man has no effect, whether he intended divorce by it or not, because divorce can only occur after marriage. We warn against obsessive thoughts (waswas) in this matter and others.