quality:corruption, quality:correction, linguistic:voice_change, structural:expansion
Early biographies

Important sources regarding Muhammad's life may be found in the historic works by writers of the 2nd and 3rd centuries of the Hijri era (around the 8th and 9th century CE respectively). These include traditional Muslim biographies of Muhammad, which provide additional information about his life.

The earliest written sira (biographies of Muhammad and quotes attributed to him) is Ibn Ishaq 's Life of God's Messenger written c. 767 CE (150 AH). Although the original work was lost, this sira survives as extensive excerpts in works by Ibn Hisham and to a lesser extent by Al-Tabari. However, Ibn Hisham wrote in the preface to his biography of Muhammad that he omitted matters from Ibn Ishaq's biography that "would distress certain people". Another early historical source is the history of Muhammad's campaigns by al-Waqidi (d. 207 AH), and the work of Waqidi's secretary Ibn Sa'd al-Baghdadi (d. 230 AH). Due to these early biographical efforts, more is known about Muhammad than almost any other founder of a major religion.

Many scholars accept these early biographies as authentic. However, Waqidi's biography has been widely criticized by Islamic scholars for his methods, in particular his decision to omit his sources. Recent studies have led scholars to distinguish between traditions touching legal matters and purely historical events. In the legal group, traditions could have been subject to invention while historic events, aside from exceptional cases, may have been subject only to "tendential shaping". Other scholars have criticized the reliability of this method, suggesting that one cannot neatly divide traditions into purely legal and historical categories. Western historians describe the purpose of these early biographies as largely to convey a message, rather than to strictly and accurately record history.