History of the Arabs and Islam Series - Umar Ibn Abd al-Aziz - the Fifth Rashidun Caliph, by Iraqi historian Dr. Saleh Ahmed al-Ali (1918-2003). This work deals with the personal of Omar ibn Abd al-Aziz, who upheld the truth and eliminated falsehood, only match by his four predecessors. It sheds light on his fame and standing among Muslims resulting from his prominent achievements in the vast Islamic state.