The Islamic State (ISIS) attack in Medina shows once and for all that ISIS is not Islamic, right? After all, how could a Muslim group, much less a self-styled “caliphate,” set off a bomb in the city of Muhammad himself? That proves that ISIS has nothing to do with Islam, no?

Maher Zain, a Multi Platinum-winning singer and songwriter who is Muslim, wrote on Twitter to his 1.47 million followers: “Still need proof that ISIS is the foremost enemy of Islam? They attack the Prophet’s City. Terror knows no religion!” Boxer Amir Khan tweeted to his 1.75 million followers: “The attack in our beloved Prophet Muhammad’s city Madinah proves that Isis has no religion!” The UK Muslim broadcaster Mohammed Shafiq wrote: “The attack on #Madinah was an attack against all Muslims. We need unity against this evil.”

And the Qur’an forbids Muslims to kill other Muslims (4:92). But Islam also mandates death for those who are considered heretics and apostates – and the Islamic State, in claiming to be the caliphate, the one true government to which all Muslims owe allegiance, and in demanding the obedience of all Muslims worldwide, has placed itself in the position of considering any Muslims who reject its authority to be heretical by virtue of that very rejection, and therefore worthy of death.

That is all the more true regarding governments of Muslim states that do not accept the caliphate. The Islamic State regards the House of Saud as illegitimate, and therefore to undermine it is a holy act. Reuters reported Sunday that the Islamic State jihadis targeted “a security headquarters at a mosque in the holy city of Medina,” and that “a suicide bomber detonated a bomb near the security headquarters of the Prophet’s Mosque in Medina, the second-holiest site in Islam. Saudi-owned al-Arabiya television said an initial death toll from the Medina blast included three suicide bombers and two security forces officers.”