Umar ibn al-Khattab (Arabic: عُمَر بْن ٱلْخَطَّاب; c. 583 – November 644) was the second caliph, ruling from August 634 until his assassination in November 644. A prominent companion and father-in-law of the Prophet Muhammad, Umar succeeded Abu Bakr (r. 632–634) as the second caliph. Born into the Banu Adi, Umar initially opposed Muhammad, his distant Qurayshite kinsman and later son-in-law.