Abu Bakr As-Ṣiddīq (real name Abdullah ibn Abi Quhafa)  popularly known by his nickname Abū Bakr  was a senior companion (Sahabi) and the father-in-law of the Islamic prophet Muhammad. He ruled over the Rashidun Caliphate from 632–634 CE when he became the first Muslim Caliph following Muhammad's death.  As Caliph, Abu Bakr succeeded to the political and administrative functions previously exercised by Muhammad. He was called Al-Siddiq (The Truthful)  and was known by that title among later generations of Muslims.