Sahih Bukhari Volume 002, Book 022, Hadith Number 314.
Narated By Abu Huraira : People say that I narrate too many narrations of the Prophet; once I met a man (during the life-time of the Prophet) and asked him, "Which Sura did Allah's Apostle s recite yesterday in the 'Isha' prayer?" He said, "I do not know." I said, "Did you not attend the prayer?" He said, "Yes, (I did)." I said, "I know. He recited such and such Sura."