Abū Bakr aṣ-Ṣiddīq ‘Abdallāh bin Abī Quḥāfah (Arabic: أبو بكر الصديق عبد الله بن أبي قحافة; c. 573 CE – 23 August 634 CE), popularly known as Abu Bakr (أبو بكر), was a senior companion (Sahabi) and—through his daughter Aisha—a father-in-law of the Islamic prophet Muhammad. Abu Bakr became the first openly declared Muslim outside Muhammad's family. Abu Bakr served as a trusted advisor to Muhammad. During Muhammad's lifetime, he was involved in several campaigns and treaties.Shortly before Muhammad's death in 632, Abu Bakr was one of many who pledged allegiance to Ali ibn Abi Talib at the event of Ghadir Khumm. However, after Muhammad passed away, Abu Bakr and some others gathered at a place known as Saqifa, where Umar pledged allegiance to Abu Bakr.