It was narrated that ‘Abdullah said:
“The Messenger of Allah ﷺ prayed, and he added or omitted something.” (One of the narrators) Ibrahim said: “The confusion stems from me (i.e., he was not sure which it was).” “It was said to him: ‘O Messenger of Allah! Has something been added to the prayer?’ He said: ‘I am only human, I forget just as you forget. If anyone forgets, let him perform two prostrations when he is sitting (at the end).’ Then the Prophet ﷺ turned and prostrated twice.”

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ عَامِرِ بْنِ زُرَارَةَ، حَدَّثَنَا عَلِيُّ بْنُ مُسْهِرٍ، عَنِ الأَعْمَشِ، عَنْ إِبْرَاهِيمَ، عَنْ عَلْقَمَةَ، عَنْ عَبْدِ اللَّهِ، قَالَ صَلَّى رَسُولُ اللَّهِ ﷺ فَزَادَ أَوْ نَقَصَ - قَالَ إِبْرَاهِيمُ وَالْوَهْمُ مِنِّي - فَقِيلَ لَهُ يَا رَسُولَ اللَّهِ أَزِيدَ فِي الصَّلاَةِ شَىْءٌ قَالَ " إِنَّمَا أَنَا بَشَرٌ أَنْسَى كَمَا تَنْسَوْنَ فَإِذَا نَسِيَ أَحَدُكُمْ فَلْيَسْجُدْ سَجْدَتَيْنِ وَهُوَ جَالِسٌ " . ثُمَّ تَحَوَّلَ النَّبِيُّ ﷺ فَسَجَدَ سَجْدَتَيْنِ .