Mocking at the Religion
Allah (swt) said, -meaning- {If you does question them, they declare (with emphasis); “We were only talking idly and in play. “ Say (O Muhammad (saw): “Was it at Allah, and His Signs, and His Messenger, that you were mocking?”}.
As a matter of fact, mocking at something that the Prophet has been sent with is disbelief by consensus of Islamic scholars, even if he did not mean to mock really, such as being joking.
Ibn Jarir, Ibn Hatem, Abu Ash-Sheikh, and others reported that Abdu-LLah bin Omar said, ‘a man in Tabuk Battle once said, “I have not ever seen such people like our Qur’an readers, they are gluttonous coward liars”, another man then replied, “you have lied! But rather you are a hypocrite, I shall inform the Messenger of Allah (saw)”.
So the Prophet knew about that man and a Qur’anic Ayah (Verse) then descended’. Ibn Omar then said, ‘I saw that man then hanging himself (begging) by the Prophet’s camel noseband (with stones being fallen at him) and saying, “O Messenger of Allah, I was only talking idly and joking!” and the Prophet replying repeatedly, -meaning- {Say ( O Muhammad (saw): “Was it at Allah, and His Signs, and His Messenger, that you were mocking?”}
Therefore , whosoever mocks at something, which the Prophet has been sent with, is a disbeliever. Such as mocking learning Islamic Legislation or at its people, mocking at the Reward and the Punishment of Allah, or mocking at those who enjoin Al-Ma’ruf (Islamic Monotheism and all that Islam has ordained) and forbid Al-Munkar (Polytheism, disbelief and all that Islam has forbidden) is disbelief as well. Or whosoever mocks at Prayers or those who perform Prayers, mocking at those who let their beards grow, or those who leave practicing Ar-Riba (usury) is a disbeliever.
Every Muslim should be severe with those who mock at his Religion even if he was a close relative, and he should not sit with him lest he should be considered one of them, for Allah (swt) said, -meaning- {Already has He sent you word in the Book, that when you hear the Signs of Allah held in defiance and ridicule, you are not to sit with them unless they turn to a different theme. If you did, you would be like them. For Allah will collect the Hypocrites and those who defy faith, all in Hell}.