Abu Bakr (c. 573-634) is, in the Sunni account, the first adult free man to accept Islam and the closest of the Prophet Muhammad's companions. A respected Meccan merchant of the Quraysh, he is remembered by the honorific al-Siddiq, the truthful, and as the father of Aisha, whom the Prophet married. He is the second of the two who sheltered in the cave during the migration to Medina, a moment the Qur'an is traditionally read as commemorating.
As with all the earliest Islamic history, the sources stand at a distance from the events. The narrative material comes from the sira and hadith literature, the biography of Ibn Ishaq in Ibn Hisham's later recension, and the ninth-century collections of al-Bukhari and Muslim, written down generations after the first Muslims and evaluated within the tradition through the science of the chains of transmission.
Across that literature Abu Bakr is portrayed as steadfast, austere and self-effacing, the man who ransomed persecuted slaves who had converted and who steadied the community at moments of crisis. When Muhammad died in 632, it was Abu Bakr who, by the tradition, addressed the stunned Muslims: whoever worshipped Muhammad, Muhammad is dead; whoever worships God, God is living and does not die.