development of the Ibadhi doctrine, the growth of their organization, and the rapid expansion of their movement in Yemen, Oman, Khurasan, and North Africa is undoubtedly due to Abu 'Ubaidah, and his gifted abilities both as a scholar and statesman.7 He played the greatest part as the most successful leader of the Ibadhi movement during the last period of the 'Umayyad rule and the beginning of the 'Abbasid rule. Shammakhi reported that Abu 'Ubaidah died during the Caliphate of Abu Ja'far al-Mansur (136-158).8 It is already mentioned that he lived for eighty years which he spent in learning and teaching. It can be said, therefore, that Abu 'Ubaidah lived in the period starting with the end of the first half of the first century up to the end of the first half of the second century. It is also suggested that he became the leader of the Ibadhi movement after he was released from prison in the year 95, two years after the death of Jabir b. Zaid.9

To understand the distinctive character of Abu 'Ubaidah and the aspect which distinguished his personality, one must refer to the influence of his different teachers. First there was 'Urwah b. 'Udayyah, a strong and pious man of great experience of religious and political conflict which took place during the civil wars between 'Ali and Mu'awiyah. He was the first man to reject arbitration and fought against 'Ali in the battle of al-Nahrawan; he was later killed by 'Ubaidullah b. Ziyad. The servant of 'Urwah described him to 'Ubaidullah as follows: "I never prepared his bed for him at night, nor brought him food during the day;"10 meaning that he always fasts during the days, and spends the nights praying. Abu 'Ubaidah, being a client of 'Urwah must have been influenced by him a great deal. His other teacher Suhar al-'Abdi was a great orator (Khatib), great genealogist, and author of a book on 'Amthal,11 (proverbs), as well as a theologian.12 His teacher Jabir b. Zaid was a great Jurist, and an eminent Traditionalist; Abu 'Ubaidah, having studied under these great men, possessed all the various qualities they had. He was an ascetic, pious worshipper,13 a brilliant orator,14 an excellent teacher, and great scholar, covering fields of theology, Jurisprudence, and Traditions. And, finally, he had an excellent organizing ability.

In the field of Ibadhi doctrine, Abu 'Ubaidah kept to the same method as Jabir b. Zaid, but he contributed more theological opinion in order to face the rising problems in this field. This may also be due to the influence of his teacher Suhar al-'Abdi. In his legal opinions, Abu 'Ubaidah kept to the same line as his predecessor, Jabir b. Zaid, of whom he was very proud, as he said, "Every man of Traditions (sahib hadith) who has no Imam in jurisprudence is gone astray. If God had not favoured us with Jabir b. Zaid we too would have gone astray."15 He also kept the same respect for the Companions and their opinions. He said, "He who has no teacher among the companions possesses nothing of the religion. God has favoured us with 'Abdullah b. 'Abbas b. 'Abd al-Muttalib,