Alfred Guillaume (Islam, 1954, blz. 120):
The Shi'a very soon split up into a number of sects...The most important of these is the 'Twelvers' or 'Imamites', who form a large community to this day. They recognize twelve Imams in the Ali-Fatima line which ends with Muhammad al- Mahdi. He disappeared from the world in 880 and is believed to be preserved against the day of his second coming as Mahdi ( a word which means 'guided one'), the hidden Imam whom the faithful await to restore justice and righteousness to the world
Alfred Guillaume (Islam, 1954, blz. 117):
"A man named Mukhtar headed a revolt in the name of Muhamad al-Hanafiya,
son of Ali by a wife other than Fatima, and though he failed in his attemt his
rising had an important sequel. He gave out that this Muhammad (al-Hanafiya) was
not dead but had retired into concealment in the mountains around Mecca, and
the faithful must expect his second coming to restore peace and
justice to the world. Such was the birth of the Mahdi legend, which has give
rise to countless pretenders down to modern times.
...There is a large apocalyptic literature concerned with calaculations as to when the Redeemer may be expected. In later Sunni tradition the Mahdi is Jesus who will, when he returns to the earth, slay the anti-Christ. Ibn Khaldoun, one of the greatest thinkers that Islam has produced, says outright that the belief in the coming of the Mahdi is of popular origin. He knows no trustworthy authority for it.