An Excellent Article: [ISIS] Ibn Kathir: If The Khawarij Ever Gained Strength in Iraq & Syria, There Would Be Mass Killing
See Link
http://www.abukhadeejah.com/isis-in-iraq-syria-ibn-kathir-died-774-ah-if-the-khawaarij-ever-gained-strength-in-iraq-and-syria-there-would-be-mass-killing/