Abu Bakr (Abdullah ibn Abi Quhafa) (Arabic: عبد الله بن أبي قحافة, Transliteration: ʿAbd Allāh ibn Abī Quḥāfah, c. 573 CE – 23 August 634 CE) also known as Abū Bakr as-Șiddīq (Arabic: أبو بكر الصديق) 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, since the religious function and authority of prophethood ended with Muhammad's death according to Islam. He was called Al-Siddiq (The Truthful) and was known by that title among later generations of Muslims.
As a young man, Abu Bakr became a cloth merchant and he traveled extensively in Arabia and neighboring lands in the Middle East, through which he gained both wealth and experience. He eventually came to be recognized as the chief of his clan. On his return from a business trip to Yemen, he was informed that in his absence Muhammad had openly declared his prophethood. Not long after, Abu Bakr accepted Islam and was the first person outside the family of Muhammad to openly become a Muslim. He was instrumental in the conversion of many people to the Islamic faith and early in 623, Abu Bakr's daughter Aisha was married to Muhammad, strengthening the ties between the two men.
Abu Bakr served as a trusted advisor and close friend to Muhammad. During the lifetime of Muhammad, he was involved in several campaigns such as the Battle of Uhud, the Battle of the Trench, the Invasion of Banu Qurayza, Battle of Khaybar, the Conquest of Mecca, the Battle of Hunayn, the Siege of Ta'if, and the Battle of Tabuk where he was reported to have given all of his wealth for the preparation of this expedition. He also participated in the Treaty of Hudaybiyyah and was made one of the witnesses over the pact.
Abu Bakr's Caliphate lasted for a little over two years (or 27 months), ending with his death after an illness. Though the period of his caliphate was not long, it included successful invasions of the two most powerful empires of the time, a remarkable achievement in its own right. He set in motion a historical trajectory that in few decades would lead to one of the largest empires in history.
Read more about Abu Bakr: Lineage and Title, Early Life, Migrations To Abyssinia, 615, Last Years in Mecca, Migration To Medina, Death of Muhammad, Other Ahadith On The Virtues of Abu Bakr, Election of Abu Bakr To Caliphate, Reign As A Caliph, Death, Legacy, Hadith Transmitted By Him