Another great historical movement, headed by a leader who proclaimed himself the mandi (Mahommed ibn Abdallah ibn Tumart), was that of the Almohades.
On the Arab invasion this work was in great danger of perishing at the hands of the iconclastic caliph Omar and his generals, but it was fortunately preserved; and we find it in the 2nd century of the Hegira being paraphrased in Arabic by Abdallah ibn el Mokaffa, a learned Persian who had embraced Islam.
Abdallah, was converted from Zoroastrianism to Islam.
Abdallah, had four sons who rendered distinguished services to Mamun.
As a reward for his services Abdallah was appointed governor of Jebel Shammar, and had already established himself in Hail when the Egyptian expedition of 1836 removed Fesal temporarily from Nejd.