On Friday, worshippers at a Sufi Mosque in Egypt suffered a brutal terrorist attack.
At least 235 people were killed and hundreds more wounded as bombers detonated explosives and gunmen attacked first responders as they sought to save the wounded.
It seems very likely that the Islamic State or a Salafi jihadist affiliate was responsible.
But in that case, why would Muslims show such brutality to a different sect from their faith?
The answer is simple: purity.
Put simply, Salafi jihadists in the ISIS breed believe they are on a mission to liberate the Earth from anyone who does not kneel to their theology. While this includes atheists and those who subscribe to different faiths, ISIS retains a particular hatred for Muslims who do not accept its narrative. They believe those Muslims are betrayers of the faith, traitors against God's gift of life in return for fealty.
But where Salafi jihadists hate Shia Muslims for reasons of historical and theological divergence, they hate Sufi Muslims for their unique approach towards worship. Specifically, ISIS and other Salafi jihadists despise Sufis for their belief that God is reachable in a personal, almost informal manner. Where Salafists view Allah as existing in necessary separation from individuals on Earth, Sufis seek to form individual communion with God via their acts of worship.
It is totally absurd, but these rationales give Salafi jihadists a sense of moral purpose in slaughtering innocent worshipers.