Al-Abbas was a grandson of Isa ibn Musa, the nephew of the first two Abbasid caliphs as-Saffah and al-Mansur and initial heir-apparent to the latter. Shortly after the ascension of Harun al-Rashid in 786 he is mentioned as serving as deputy governor of Kufa for his father Musa, and later in Harun's reign he was appointed as full governor of that same city.[1] In 805 he led the annual pilgrimage,[2] and he also served as governor of Mecca at an unspecified date.[3]