Sahih Muslim 572
Sahih Muslim · Book 5: The Book of Mosques and Places of Prayer · As-Sahw (forgetfulness) in prayer and prostrating to compensate for it
Abdullah reported:
وَحَدَّثَنِي الْقَاسِمُ بْنُ زَكَرِيَّاءَ ، حَدَّثَنَا حُسَيْنُ بْنُ عَلِيٍّ الْجُعْفِيُّ ، عَنْ زَائِدَةَ ، عَنْ سُلَيْمَانَ ، عَنْ إِبْرَاهِيمَ ، عَنْ عَلْقَمَةَ ، عَنْ عَبْدِ اللَّهِ ، قَالَ صَلَّيْنَا مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم فَإِمَّا زَادَ أَوْ نَقَصَ - قَالَ إِبْرَاهِيمُ وَايْمُ اللَّهِ مَا جَاءَ ذَاكَ إِلاَّ مِنْ قِبَلِي - قَالَ فَقُلْنَا يَا رَسُولَ اللَّهِ أَحَدَثَ فِي الصَّلاَةِ شَىْءٌ فَقَالَ " لاَ " . قَالَ فَقُلْنَا لَهُ الَّذِي صَنَعَ فَقَالَ " إِذَا زَادَ الرَّجُلُ أَوْ نَقَصَ فَلْيَسْجُدْ سَجْدَتَيْنِ " . قَالَ ثُمَّ سَجَدَ سَجْدَتَيْنِ .
We prayed along with the Messenger of Allah (may peace he upon him) and he committed or omitted (something). Ibrahim said: By Allah, this is a misgiving of mine only. We said: Messenger of Allah, is there something new about the prayer? He (the Holy Prophet) said: No. We told him about what he had done. He (the Holy Prophet) said: When a man commits or omits (something in prayer), he should perform two prostrations, and he then himself performed two prostrations.