Quran
A folio from an early Quran, written in Kufic script (Abbasid period, 8th–9th century).
The Quran is the central religious text of Islam and Muslims believe that it represents the words of God revealed to Muhammad through the archangel Gabriel. Although it mentions Muhammad directly only four times, there are verses which can be interpreted as allusions to Muhammad's life. The Quran however provides little assistance for a chronological biography of Muhammad, and many of the utterances recorded in it lack historical context.
Early biographies
Main article: Prophetic biography
Next in importance are historical works by writers of the 3rd and 4th centuries of the Muslim era. These include the traditional Muslim biographies of Muhammad (the sira literature), which provide further information on Muhammad's life.
The earliest surviving written sira (biographies of Muhammad and quotes attributed to him) is Ibn Ishaq's Life of God's Messenger written ca. 767 (150 AH). The work is lost, but was used verbatim at great length by Ibn Hisham and Al-Tabari. Another early source is the history of Muhammad's campaigns by al-Waqidi (death 207 of Muslim era), and the work of his secretary Ibn Sa'd al-Baghdadi (death 230 of Muslim era).
Many scholars accept the accuracy of the earliest biographies, though their accuracy is unascertainable. Recent studies have led scholars to distinguish between the traditions touching legal matters and the purely historical ones. In the former sphere, traditions could have been subject to invention while in the latter sphere, aside from exceptional cases, the material may have been only subject to "tendential shaping".
Hadith
In addition, the hadith collections are accounts of the verbal and physical traditions of Muhammad that date from several generations after his death.
Western academics view the hadith collections with caution as accurate historical sources. Scholars such as Madelung do not reject the narrations which have been compiled in later periods, but judge them in the context of history and on the basis of their compatibility with the events and figures.
Non-Arabic sources
The earliest documented Christian knowledge of Muhammad stems from Byzantine sources. They indicate that both Jews and Christians saw Muhammad as a "false prophet". In the Doctrina Jacobi nuper baptizati of 634, Muhammad is portrayed as being "deceiving[,] for do prophets come with sword and chariot?, [...] you will discover nothing true from the said prophet except human bloodshed." Another Greek source for Muhammad is the 9th-century writer Theophanes. The earliest Syriac source is the 7th-century writer John bar Penkaye.
