Umar ibn al-Khattab (Arabic: عُمَر بْن ٱلْخَطَّاب, romanized: ʿUmar ibn al-Khaṭṭāb; c. 584 – 644), also spelled Omar, was the second Rashidun caliph, ruling from August 634 until his assassination in 644. He succeeded Abu Bakr (r. 632–634) and is regarded as a senior companion and father-in-law of the Islamic prophet Muhammad.
Initially, Umar opposed Muhammad, who was his distant Qurayshite kinsman. However, after converting to Islam in 616, he became the first Muslim to openly pray at the Kaaba. He participated in nearly all of Muhammad’s battles and expeditions, and Muhammad conferred upon him the title al-Fārūq ("the Distinguisher") for his sound judgement. After Muhammad’s death in June 632, Umar pledged allegiance to Abu Bakr as the first caliph and served as his chief adviser. In 634, shortly before his death, Abu Bakr nominated Umar as his successor.
