As part of his biographical series on the great men of Islam, Dr. Sallabi gives us a detailed portrait of the eighth Umayyad caliph, ' Umar ibn Abdul-'Aziz . The reader will discover throughout the pages his immense piety and his concern for justice which earned him the title of fifth Rightly Guided Caliph, in the wake of Abu Bakr , ' Umar , 'Uthman and ' Alî .