It is said that there was none, among the Khalifs of the house of Abbas, more accomplished in all branches of knowledge than El Mamoun. On two days in each week, he was wont to preside at conferences of the learned, when the doctors and theologians met and sitting, each in his several rank and room, disputed in his presence. One day, as he sat thus, there came into the assembly a stranger, clad in worn white clothes, and sat down in an obscure place, behind the doctors of the law. Then the assembled scholars began to speak and expound difficult questions, it being the custom that the various propositions should be submitted to each in turn and that whoso bethought him of some subtle addition or rare trait, should make mention of it. So the question went round till it came to the stranger, who spoke in his turn and made a goodlier answer than that of any of the doctors; and the Khalif approved his speech and bade advance him to a higher room. When the second question came round to him, he made a still more admirable answer, and the Khalif ordered him to be preferred to a yet higher place. When the third question reached him, he made answer more justly and appropriately than on the two previous occasions, and El Mamoun bade him come up and sit near himself. When the conference broke up, water was brought and they washed their hands; after which food was set on and they ate. Then the doctors arose and withdrew; but El Mamoun forbade the stranger to depart with them and calling him to himself, entreated him with especial favour and promised him honour and benefits.

Presently, they made ready the banquet of wine; the fair-faced boon-companions came and the cup went round amongst them. till it came to the stranger, who rose to his feet and said, 'If the Commander of the Faithful permit me, I will say one word.' 'Say what thou wilt,' answered the Khalif. Quoth the stranger, 'Verily, the Exalted Intelligence (11) (whose eminence God increase!) knoweth that his slave was this day, in the august assembly, one of the unknown folk and of the meanest of the company, and the Commander of the Faithful distinguished him and brought him near to himself, little as was the wit he showed, preferring him above the rest and advancing him to a rank whereto his thought aspired not: and now he is minded to deprive him of that small portion of wit that raised him from obscurity and augmented him, after his littleness. God forfend that the Commander of the Faithful should envy his slave what little he hath of understanding and worth and renown! But, if his slave should drink wine, his reason would depart from him and ignorance draw near to him and steal away his good breeding; so would he revert to that low degree, whence he sprang, and become contemptible and ridiculous in the eyes of the folk. I hope, therefore, that the August Intelligence, of his power and bounty and royal generosity and magnanimity, will not despoil his slave of this jewel.'

When the Khalif heard his speech, he praised him and thanked him and making him sit down again in his place, showed him high honour and ordered him a present of a hundred thousand diners. Moreover he mounted him upon a horse and gave him rich apparel; and in every assembly he exalted him and showed him favour over all the other doctors, till he became the highest of them all in rank.