Uthman ibn Affan, the third caliph, was chosen by a council meeting in Medina, in northwestern Arabia, in AH 23 (643/644). The second caliph, Umar ibn al-Khattab, was stabbed by Piruz Nahavandi, a Persian slave. Mindful of the tumults that had occurred after the death of Muhammad (see Succession to Muhammad), on his deathbed Umar appointed a committee of six men, to choose a new leader.