What is the ruling regarding the action of a son who slapped his father because he blasphemed Allah?

We appreciate the son's zeal for his religion and his anger at the violation of God's sanctities, which is a sign of his faith. If the son struck his father in a state of extreme anger where he lost consciousness, then there is no blame upon him, Allah willing, because a person is not held accountable if his mind is overwhelmed. However, if he was conscious, then he is sinful and must repent. He must be dutiful to his father and treat him kindly, even if he is a disbeliever, as Allah Almighty said: {But if they endeavor to make you associate with Me that of which you have no knowledge, do not obey them but accompany them in [this] world with appropriate kindness.} The father must be advised to repent sincerely and perform many righteous deeds, for cursing Allah Almighty is a grave sin and disbelief by the consensus of scholars.