Who was he?
Abdullah ibn Ibadh al-Murri al-Tamimi , after who is named the Ibadhi school, belonged to Murrah, a clan of the major tribe of Tamim. The school was named after his father because he was better known than the son, as is the case in Arabic genealogy. Al-Malati alone reported that the sect was named after its founder who is, according to him, Ibadh b. 'Amr. This information cannot be taken into account, for al-Malati reported information about the Kharijites in his book contrary to all sound authorities who dealt with the subject.
Reports about Ibn Ibadh are scarce and very little is known about him in both Ibadhi and non-Ibadhi sources. He is of Banu Sarim b. al-Harith b. Muqa'is of Banu Tamim, one of the main tribes of Mudar. Nothing is known about his early life. However, Muhammad b. Yusuf Atfaiyish, a prominent contemporary Ibadhi scholar suggests that Ibn Ibadh moved from Najd, the homeland of his tribe, to Basrah. He also reported that certain narrations state that he was a 'Sahabi (a companion) for a short time. However, most reliable Ibadhi sources consider him to belong to the class of al-Tabi'aun who lived during the second half of the first century H. It is not known whether he took any active part in the civil wars which occurred among Muslims before the 'Umayyad rule. But it appears that he was not satisfied by the rule of Mu'awiyah and criticizing certain practices that he believed to be contrary to the Qur'an and the Sunnah.