The earliest Muslim source of information for the life of Muhammad, the Quran, gives very little personal information and its historicity is debated. Prophetic biography, known as "sīra", along with records of the words, actions, and the silent approval of Muhammad, known as "hadith", survive in the historical works of writers from the third and fourth centuries of the Muslim era (c. 800−1000 CE), and give a great deal of information on Muhammad, but the reliability of this information is very much debated. In addition there are a relatively small number of contemporaneous or near-contemporaneous non-Muslim sources which confirm the existence of Muhammad and are valuable both in themselves and for comparison with Muslim sources.