Abd Allah ibn Ibad al-Tamimi (; died ) was an Arab Islamic scholar and a leader of the Kharijites from Basra, of the tribe of Banà « Saÿd of Tamëm. In traditional Islamic historiography, he is the founder and eponym of IbÃÂá¸Âësm.
Ibn IbÃÂḠwas one of the group of Basran Kharijites who, led by NÃÂfëÿ ibn al-Azraq, joined the defenders under ÿAbd AllÃÂh ibn al-Zubayr at the siege of the Kaÿba by the Umayyads in 683. After the siege was lifted, the Kharijites were disappointed by Ibn al-Zubayr's refusal to denounce the late Caliph ÿUthmÃÂn and returned to Basra. There they were imprisoned by the Umayyad governor ÿUbayd AllÃÂh ibn ZiyÃÂd. When the Basrans rose up and overthrew Umayyad rule, the prisoners were freed. Ibn al-Azraq led many of them to Ahvaz, denouncing the townsmen as "polytheists". Ibn IbÃÂḠremained in Basra. His father, IbÃÂḠibn ÿAmr al-Tamëmë, seems to have been the first leader of the moderates who refused to secede with Ibn al-Azraq.
Ibn IbÃÂḠsucceeded his father and wrote a defence of those Kharijites who stayed behind. By defending the Basrans against the charge of polytheism and accusing them of no more than "ingratitude", he justified the decision of true Muslims to live among them. According to Abà « Mikhnaf, who died in 774 and is the earliest source on Ibn IbÃÂá¸Â's life, Ibn IbÃÂḠalso wrote against the intermediate position of ÿAbd AllÃÂh ibn al-á¹¢affÃÂr, founder of the Sufri sect. According to al-MadÃÂþinë, Ibn IbÃÂḠalso received opposition from Abà « Bayhas, founder of the Bayhasiyya sect, who took a position closer to Ibn al-Azraq's.
The dispute over Ibn al-Azraq's hijra to Ahvaz is the last known event in Ibn IbÃÂá¸Â's life. IbÃÂá¸Âë tradition itself contains no further biographical details. It does ascribe to Ibn IbÃÂḠtwo surviving letters addressed to the Umayyad caliph ÿAbd al-Malik. Recent scholarship has questioned their authenticity. Even Ibn IbÃÂá¸Â's position as the leader of the first IbÃÂá¸Âës has come into question. His contemporary, JÃÂbir ibn Zayd (died 712), is given even greater prominence in later tradition. One of the letters ascribed to Ibn IbÃÂḠhas been reassigned to JÃÂbir ibn Zayd and its recipient identified as ÿAbd al-Malik ibn al-Muhallab, head of the Azd tribe to which JÃÂbir belonged.