It is related that a Kharijite was ushered into al-Maʾmūn’s presence. The caliph asked him, “What has moved you to rebellion?”
He answered, “The Almighty’s words: ‘And whoever does not judge by what Allah has revealed—they are the disbelievers’ (5:44).”
Al-Maʾmūn said, “Do you have certain knowledge that this verse is in fact revealed?”
“Yes.”
“And what is your proof?”
“The consensus of the ummah.”
Al-Maʾmūn replied, “Just as you were satisfied with their consensus regarding its revelation, be satisfied with their consensus regarding its interpretation.”
The man conceded, “You are right. Peace be upon you, Commander of the Faithful.” (1)

Al-Ghalābī narrates: Maḥdī ibn Sābiq told us that al-Maʾmūn once entered the land-tax bureau and noticed a strikingly handsome youth with a pen tucked behind his ear. Pleased by his appearance, he asked, “Who are you?”
The youth replied, “One reared under your rule, schooled by your refinement, and nurtured by your bounty, Commander of the Faithful—Ḥasan ibn Rajāʾ.”
Al-Maʾmūn said, “Young man, it is through spontaneous eloquence that minds outshine one another.” He then ordered his promotion and granted him one hundred thousand.

Al-Maʾmūn also said, “Three replies have left me at a loss:
“I went to console the mother of Dhū al-Riyāsatayn, al-Faḍl ibn Sahl, and said, ‘Do not grieve over him, for I shall be his substitute for you.’ She answered, ‘Commander of the Faithful, how could I not mourn a son who gained me someone like you?’
“I was brought a self-styled prophet and asked, ‘Who are you?’ He said, ‘I am Moses son of Imran.’ I said, ‘Woe to you! Moses was given signs—bring them, so that I may believe you.’ He replied, ‘I brought the miracles only to Pharaoh; if you say, as he did, “I am your supreme Lord,” I will bring you the signs.’
“And the people of Kufa came to complain about their governor, and their spokesman said, ‘He is the worst governor,’