What is the ruling on a man saying to his brother in a moment of intense anger: "You are forbidden to me just as my mother and sister are forbidden to me"? And what is the expiation for that if it is an oath? And is this considered an open oath? And what is the ruling on someone who frequently curses religion while maintaining his obligatory and supererogatory prayers?

Cursing the religion is an act of disbelief by consensus. However, there are impediments that prevent it from being considered such, such as uttering it mistakenly without intending it, or due to coercion, or misinterpretation, or ignorance. Whoever dies persisting in disbelief, their deeds are nullified. As for a brother forbidding his brother, likening him to his mother or sister, this is nonsense and nothing results from it, for ẓihār (declarations of unlawful analogy) applies only to wives. If by forbidding his brother he intended to forbid what Allah has made lawful for him, then he must seek forgiveness and, according to the majority of scholars, nothing else is incumbent upon him. The Hanafis, however, stated that an expiation for a broken oath (kaffārat yamīn) is due. Intense anger does not change the ruling as long as the person is conscious and acting by choice.