If you see that I am wrong, advise me and put me on the right track, and obey me as long as I obey God in you... God gave your mujahedeen brothers victory after long years of jihad and patience... so they declared the caliphate and placed the caliph in charge. This is a duty on Muslims that has been lost for centuries.
As quoted in "Islamic State leader Abu Bakr al-Baghdadi addresses Muslims in Mosul", The Telegraph (5 July 2014)
Islamic State leader Abu Bakr al-Baghdadi addresses Muslims in Mosul - Telegraph