علي بن موسى الرضا
When al-Ridha was summoned to Khurasan and reluctantly accepted the role of successor to al-Ma'mun, al-Ma'mun summoned the Imam's brother, Zayd, who had revolted and brought about a riot in Medina to his court in Khorasan. Al-Ma'mun kept him free as an honor to Ali al-Ridha and overlooked his punishment.