Umar ibn al-Khattab
(r. 634 – 644 )
Second Sunni caliph and Companion of Muhammad . Oversaw major expansion of the Islamic empire. Great military leader who adopted the title “Commander of the Faithful.” Transformed Arab conquerors into a separate elite military class who ruled newly conquered regions but were not permitted to engage in agriculture or commerce. Permitted conquered peoples to continue to practice their own religions, rather than insisting that they convert to Islam, provided that they paid a poll tax. Transmitted numerous hadith; considered a particularly authoritative source. Instituted the method of appointing a committee to select the next caliph; the election was to be accompanied by the clasping of hands and the exchange of oaths of allegiance to the successor.