Abu al-ʿAbbas al-Sarraj said: Muhammad ibn Sahl ibn ʿAskar related:

A stranger carrying an inkwell stepped forward to al-Maʾmun and said, “Commander of the Faithful, I am a hadith scholar who has become cut off on his journey.”

Al-Maʾmun asked him, “What do you have by heart on the subject of such-and-such?”
The man could not recall a single report.
Al-Maʾmun thereupon began, “Hushaym narrated to us, and Yahya narrated to us, and Hajjaj ibn Muhammad narrated to us …,” continuing until he had cited the entire chapter. Then he asked him about another topic, and again the man produced nothing.
So al-Maʾmun recited, “So-and-so narrated to us, and so-and-so narrated to us,” and then said to his companions, “One of them chases after hadith for three days and then proclaims, ‘I am a man of hadith!’ Give him three dirhams.” (1)

I say: He was open-handed, praised for his liberality; it is reported that in a single session he distributed twenty-six million dirhams. He used to drink the nabidh of Kufa.
Others said that he drank wine outright (2); Allah knows best.
It is also said that he once gave a Bedouin who lauded him thirty thousand dinars.

Masruq ibn ʿAbd al-Rahman al-Kindī said: Muhammad ibn al-Mundhir al-Kindī, a neighbor of ʿAbd Allah ibn Idris, told me:
When al-Rashid performed the pilgrimage and entered Kufa, only Ibn Idris and ʿIsa ibn Yunus failed to come to him. He therefore sent al-Amin and al-Maʾmun to them, and Ibn Idris related one hundred hadiths to the two of them.
Al-Maʾmun said, “Uncle, do you permit me to repeat them from memory?”
He replied, “Yes, do so.”
Al-Maʾmun repeated them, and Ibn Idris was astonished at his memorization (3). The two princes then went on to ʿIsa, who likewise narrated to them.
Al-Maʾmun ordered that ʿIsa be given ten thousand dirhams, but he refused, saying, “Not even a drink of water should be accepted in return for the hadith of the Messenger of Allah, peace and blessings be upon him.”