Sahih al-Bukhari 1223
Sahih al-Bukhari · Book 21: Actions while Praying · Thinking of something during As-Salat (the prayer)
Narrated Abu Huraira:
حَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى ، حَدَّثَنَا عُثْمَانُ بْنُ عُمَرَ ، قَالَ أَخْبَرَنِي ابْنُ أَبِي ذِئْبٍ ، عَنْ سَعِيدٍ الْمَقْبُرِيِّ ، قَالَ قَالَ أَبُو هُرَيْرَةَ ـ رضى الله عنه ـ يَقُولُ النَّاسُ أَكْثَرَ أَبُو هُرَيْرَةَ، فَلَقِيتُ رَجُلاً فَقُلْتُ بِمَ قَرَأَ رَسُولُ اللَّهِ صلى الله عليه وسلم الْبَارِحَةَ فِي الْعَتَمَةِ فَقَالَ لاَ أَدْرِي. فَقُلْتُ لَمْ تَشْهَدْهَا قَالَ بَلَى. قُلْتُ لَكِنْ أَنَا أَدْرِي، قَرَأَ سُورَةَ كَذَا وَكَذَا.
People say that I narrate too many narrations of the Prophet; once I met a man (during the lifetime of the Prophet) and asked him, "Which Sura did Allah's Messenger (ﷺ) 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."