Question: Ubaydallah ibn Abdallah ibn Tahir was the last major Tahirid to hold high office in what dynasty?
Sentence (from "Muttalib ibn Abdallah ibn Malik"): In 811, he administered the oath of allegiance ("bay'ah") to al-Ma'mun for Mosul, and was named governor of Egypt briefly in 813 and again in 814–816.
Relevant evidence: No