Who is abu bakir?

Abu Bakr As-Siddiq (Abdallah ibn Abi Quhafa) (573 CE – 23 August 634) was Muhammad's father-in-law, closest companion and adviser, who succeeded to the Prophet's political and administrative functions, thereby initiating the office of the caliphate. He was also the first convert to Islam, after Khadija, Muhammad's first wife. Muhammad conferred on him the title Siddiq, the veracious, for his power to discern the truth. Upon Muhammad's death he became the first Muslim ruler (632–634), regarded in Sunni Islam as the first of the Rashidun (righteously guided Caliphs). In Shia Islam, he is, however, regarded as a usurper and political opportunist. His caliphate lasted two years and three months, during which time he consolidated the Muslim state.