What he said after praying the wrong number
They asked whether something in the prayer had changed.
إِنَّهُ لَوْ حَدَثَ فِي الصَّلاَةِ شَىْءٌ لَنَبَّأْتُكُمْ بِهِ، وَلَكِنْ إِنَّمَا أَنَا بَشَرٌ مِثْلُكُمْ، أَنْسَى كَمَا تَنْسَوْنَ، فَإِذَا نَسِيتُ فَذَكِّرُونِي
Innahu law ḥadatha fi-ṣ-ṣalāti shayʾun la-nabbaʾtukum bih. Wa lākin innamā anā basharun mithlukum, ansā kamā tansawn, fa-idhā nasītu fa-dhakkirūnī
“If anything had changed in the prayer I would have told you. But I am only a human being like you. I forget as you forget. So when I forget, remind me.”
Where this comes from
He had prayed five and they mentioned it. He asked what it was, they told him, and he turned and made two prostrations. Then he said this.
The full narration
Narrated `Abdullah:The Prophet (ﷺ) prayed (and the sub-narrator Ibrahim said, "I do not know whether he prayed more or less than usual"), and when he had finished the prayers he was asked, "O Allah's Messenger (ﷺ)! Has there been any change in the prayers?" He said, "What is it?' The people said, "You have prayed so much and so much." So the Prophet (ﷺ) bent his legs, faced the Qibla and performed two prostration's (of Sahu) and finished his prayers with Taslim (by turning his face to right and left saying: 'As-Salamu `Alaikum- Warahmat-ullah'). When he turned his face to us he said, "If there had been anything changed in the prayer, surely I would have informed you but I am a human being like you and liable to forget like you. So if I forget remind me and if anyone of you is doubtful about his prayer, he should follow what he thinks to be correct and complete his prayer accordingly and finish it and do two prostrations (of Sahu)
Source
Ṣaḥīḥ al-Bukhārī · 401
- Agreed upon as authentic (al-Bukhārī / Muslim)