that Allah's Prophet led them in the Zuhr prayer and he offered either more or less rakʿat, and it was said to him, "O Messenger of Allah ﷺ ! Has the prayer been reduced, or have you forgotten?" He asked, "What is that?" They said, "You have prayed so many rakʿat." So he performed with them two more prostrations and said, "These two prostrations are to be performed by the person who does not know whether he has prayed more or less (rakʿat) in which case he should seek to follow what is right. And then complete the rest (of the prayer) and perform two extra prostrations."  

أَنَّ نَبِيَّ اللَّهِ ﷺ صَلَّى بِهِمْ صَلاَةَ الظُّهْرِ فَزَادَ أَوْ نَقَصَ مِنْهَا قَالَ مَنْصُورٌ لاَ أَدْرِي إِبْرَاهِيمُ وَهِمَ أَمْ عَلْقَمَةُ قَالَ قِيلَ يَا رَسُولَ اللَّهِ أَقَصُرَتِ الصَّلاَةُ أَمْ نَسِيتَ قَالَ وَمَا ذَاكَ قَالُوا صَلَّيْتَ كَذَا وَكَذَا قَالَ فَسَجَدَ بِهِمْ سَجْدَتَيْنِ ثُمَّ قَالَ هَاتَانِ السَّجْدَتَانِ لِمَنْ لاَ يَدْرِي زَادَ فِي صَلاَتِهِ أَمْ نَقَصَ فَيَتَحَرَّى الصَّوَابَ فَيُتِمُّ مَا بَقِيَ ثُمَّ يَسْجُدُ سَجْدَتَيْنِ