Title: Risālat wilāyat al-ʻahd bayn al-Khalīfah al-Maʼmūn wa al-Imām al-Riḍā
Subjects: Kings and rulers, Succession
Places: Islamic Empire
People: Maʼmūn Caliph (786-833), ʻAlī al-Riḍā ibn Mūsá (-818 or 819)