Sahih Bukhari Volume 003, Book 039, Hadith Number 540.
Narated By Abu Huraira : The people say that Abu Huraira narrates too many narrations. In fact Allah knows whether I say the truth or not. They also ask, "Why do the emigrants and the Ansar not narrate as he does?" In fact, my emigrant brethren were busy trading in the markets, and my Ansar brethren were busy with their properties. I was a poor man keeping the company of Allah's Apostle and was satisfied with what filled my stomach. So, I used to be present while they (i.e. the emigrants and the Ansar) were absent, and I used to remember while they forgot (the Hadith). One day the Prophet said, "Whoever spreads his sheet till I finish this statement of mine and then gathers it on his chest, will never forget anything of my statement." So, I spread my covering sheet which was the only garment I had, till the Prophet finished his statement and then I gathered it over my chest. By Him Who had sent him (i.e. Allah's Apostle) with the truth, since then I did not forget even a single word of that statement of his, until this day of mine. By Allah, but for two verses in Allah's Book, I would never have related any narration (from the Prophet). (These two verses are): "Verily! Those who conceal the clear signs and the guidance which we have sent down... (up to) the Merciful.' (2.159-160)