Reference: al-Hifth – Ahammiyyatuhu, ‘Ajaa.ibuhu, Tareeqatuhu, Asbaabuhu – Page 18
Tathkiratul-Huffaaz – Volume 1, Page 281
al-Bidaayah wan-Nihaayah – Volume 14, Page 14
‘Abdullaah ibn Haaroon al-Ma.moon (died 218A.H.) narrated:
al-Ameen and al-Ma.moon travelled to ‘Abdullaah ibn Idrees who narrated a hundred hadeeth to them. al-Ma.moon then said:
“O Uncle, if you permit me, I shall repeat them [all] from memory.”
So he permitted him, and he repeated them [all] from his memory as he had heard them, and Ibn Idrees was surprised at his memorisation.