Wellhausen applied biblical source-criticism techniques to Islamic history

Evidence

Instead of translating and then pasting together snippets from Arabic chronicles, which was pretty much what William Muir had done in his history of the caliphate, Wellhausen tried to sift the surviving texts and to deduce what lost original sources those texts were based on and how the historical narrative was distorted over the centuries. This, of course, was exactly what contemporary biblical scholars were doing. — Robert Irwin, For Lust of Knowing, 331