Abd al-Wahhab demanded conformity — a conformity that was to be demonstrated in physical and tangible ways. He argued that all Muslims must individually pledge their allegiance to a single Muslim leader a Caliph, if there were one. Those who would not conform to this view should be killed, their wives and daughters violated, and their possessions confiscated, he wrote. The list of apostates meriting death included the Shiite, Sufis and other Muslim denominations, whom Abd al-Wahhab did not consider to be Muslim at all. There is nothing here that separates Wahhabism from ISIS. The rift would emerge only later: from the subsequent institutionalization of Muhammad ibn ʿAbd al-Wahhab’s doctrine of “One Ruler, One Authority, One Mosque” — these three pillars being taken respectively to refer to the Saudi king, the absolute authority of official Wahhabism, and its control of “the word” i.e. the mosque. It is this rift — the ISIS denial of these three pillars on which the whole of Sunni authority presently rests — makes ISIS, which in all other respects conforms to Wahhabism, a deep threat to Saudi Arabia.
(Cartoon: Bertram, Joep. http://www.cagle.com/2014/06/mind-of-his-own/)