Ilm ar-Rijal (Arabic) is the "science of biography" especially as practiced in Islam, where it was first applied to the sira, the life of the Prophet Muhammad.

Since the sira is part of the sunnah, or moral example that Muslims are supposed to follow, and validating the sayings of Muhammad is a major study ("isnah"), accurate biography has always been of great interest to Muslims.

Another important influence of biography on Islam is in the recording of the lives of the four Rightly Guided Caliphs (a Sunni term), who expanded Islamic dominance rapidly:

• Abu Bakr Siddiq, first Caliph after Muhammad, unanimously elected by a constitutional assemly in Madina shortly after Muhammad's death in 631.
• Umar al-Khattab, nominated by Abu Bakr as his successor, and ratified by a vote in 634 after Abu Bakr's death.
• Othman bin Affan and Ali bin Talib , cousin and son-in-law of the Prophet respectively, each elected and then murdered in 656 and 661 respectively.

Ali, the last of these, is the only one considered legitimate in Shia Islam, which considers the Prophet's family to play a special holy role.

With this extremely contentious succession, and confusion about the intentions of Muhammad regarding who should rule Madina and make binding judgements in Islam, biography of these figures became a very major concern, and political bias had to be sorted out from biographical fact. During the 30 years from the death of the Prophet to the death of Ali, Islam had spread from Libya to Afghanistan, from Armenia and Sind to Gujarat, and Muslim armies had entered Spain and China. The risk of factional splintering, variant heresies regarding the life of the Prophet, and the gains that local leaders could gain by promoting such division grew to extremes.

Muslim biographers, accordingly, became expert at sorting out facts from accusations, bias from evidence, etc., and were renowned throughout the known world for their honesty in recording history - many in fact considered acknowledging faults in leaders to be a matter of religious duty, comparing their various failings to the sira or life of Muhammad. Modern practices of scientific citation and historical method owe a great deal to the rigor of early Muslims.

See also: sira, isnah, bias, biography