Umar, also spelled Omar (, born c.583 CEdied 3 November 644 CE), was one of the most powerful and influential Muslim caliphs in history. He was a senior Sahaba of the Islamic prophet Muhammad. He succeeded Abu Bakr (632–634) as the second caliph of the Rashidun Caliphate on 23 August 634. He was an expert Islamic jurist known for his pious and just nature, which earned him the epithet Al-Farooq ("the one who distinguishes between right and wrong"). He is sometimes referred to as Umar I by historians of Islam, since a later Umayyad caliph, Umar II, also bore that name. According to Sunnis, Umar is the second greatest of the Sahaba after Abu Bakr.