Sahih Muslim 572 k
'Abdullah (b. Mas'ud) reported:
The Messenger of Allah (ﷺ) led us five (rak'ahs in prayer). We said: Messenger of Allah, has the prayer been extended? He said: What is the matter? They said: You have said five (rak'ahs). He (the Holy Prophet) said: Verily I am a human being like you. I remember as you remember and I forget just as you forget. He then performed two prostrations as (compensation of) forgetfulness.
وَحَدَّثَنَاهُ عَوْنُ بْنُ سَلاَّمٍ الْكُوفِيُّ، أَخْبَرَنَا أَبُو بَكْرٍ النَّهْشَلِيُّ، عَنْ عَبْدِ الرَّحْمَنِ بْنِ الأَسْوَدِ، عَنْ أَبِيهِ، عَنْ عَبْدِ اللَّهِ، قَالَ صَلَّى بِنَا رَسُولُ اللَّهِ صلى الله عليه وسلم خَمْسًا فَقُلْنَا يَا رَسُولَ اللَّهِ أَزِيدَ فِي الصَّلاَةِ قَالَ ‏"‏ وَمَا ذَاكَ ‏"‏ ‏.‏ قَالُوا صَلَّيْتَ خَمْسًا ‏.‏ قَالَ ‏"‏ إِنَّمَا أَنَا بَشَرٌ مِثْلُكُمْ أَذْكُرُ كَمَا تَذْكُرُونَ وَأَنْسَى كَمَا تَنْسَوْنَ ‏"‏ ‏.‏ ثُمَّ سَجَدَ سَجْدَتَىِ السَّهْوِ ‏.‏