Musnad Ahmad 30:587

'Abd al-Razzaq narrated to us, Ma'mar narrated to us, from al-Zuhri, from al-A'raj, who said: Abu Hurayrah said: You say: "Abu Hurayrah narrates too much from the Prophet, may Allah bless him and grant him peace," and Allah is the place of the appointment. You say: "What is the matter with the Muhajirun that they do not narrate these hadiths from the Messenger of Allah? And what is the matter with the Ansar that they do not narrate these hadiths?" My companions among the Muhajirun were occupied by their transactions in the marketplaces, and my companions among the Ansar were occupied by their lands and tending to them. I was a poor man, and I used to sit with the Messenger of Allah, may Allah bless him and grant him peace, more than anyone else. I would be present when they were absent, and I would memorize when they forgot. The Prophet, may Allah bless him and grant him peace, said to us one day: "Whoever spreads out his garment until I finish my speech, then gathers it to himself, he will never forget anything he heard from me." So I spread out my garment—or he said: my cloak—then I gathered it to myself. By Allah, I have not forgotten anything I heard from him. By Allah, were it not for a verse in the Book of Allah, I would never have narrated anything to you. Then he recited: {Indeed, those who conceal what We sent down of clear proofs and guidance} [Al-Baqarah: 159], the entire verse.