Imam al-Rida (peace be upon him) — Ali ibn Isa said: With him was the covenant of al-Ma'mun that he had written concerning the heir-apparency of Imam al-Rida (peace be upon him), in the Imam's own handwriting... And what was on the back of the covenant in the handwriting of Imam al-Rida (peace be upon him) is this... I have made a covenant with my Allah that if I attain the caliphate and it falls to me to govern among the people, I will, among all people and especially among the Banu al-Abbas, obey Allah and His Messenger, shed no blood, and violate no one's honour, except in those cases where the limits and ordinances of Allah permit and require such an action. I will exert all my effort and endeavour in selecting those who are worthy of leadership. I have made a firm covenant for which Allah will call me to account, and He says: "And fulfil the covenant, for the covenant will be questioned about!" (al-Isra 17:34). If I make any unwarranted change or alteration, I shall deserve punishment and be liable to chastisement. I take refuge in Allah from His wrath. I hope that He Himself will grant me the ability for His worship and obedience, and that a barrier will be placed between me and disobedience to Him, provided that lies in the well-being and safety of me and the Muslims. But al-Jami'a and al-Jafr indicate the opposite of this; I do not know what will be done with me or with you (al-Ahqaf 46:9). "It is not with me. The command belongs only to Allah! He separates truth from falsehood; and He is the best of separators [of truth from falsehood]."