Sunan an-Nasa'i 1257
It was narrated that Malik bin Mighwal said:
"I heard Ash-Sha'bi say: 'Alqamah bin Qais forgot (and made a mistake) in his prayer, and they told him about that after he had spoken, He said: 'Is that true, O odd-eyed one?' He said: 'Yes.' So he undid his cloak, then he performed two prostrations of forgtfulness,and said: 'This is what the Messenger of Allah (ﷺ) did.' He said: And I heard Al-Hakam say: 'Alqamah had prayed five.'"
أَخْبَرَنَا سُوَيْدُ بْنُ نَصْرٍ، قَالَ أَنْبَأَنَا عَبْدُ اللَّهِ، عَنْ مَالِكِ بْنِ مِغْوَلٍ، قَالَ سَمِعْتُ الشَّعْبِيَّ، يَقُولُ سَهَا عَلْقَمَةُ بْنُ قَيْسٍ فِي صَلاَتِهِ فَذَكَرُوا لَهُ بَعْدَ مَا تَكَلَّمَ فَقَالَ أَكَذَلِكَ يَا أَعْوَرُ قَالَ نَعَمْ ‏.‏ فَحَلَّ حُبْوَتَهُ ثُمَّ سَجَدَ سَجْدَتَىِ السَّهْوِ وَقَالَ هَكَذَا فَعَلَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏.‏ قَالَ وَسَمِعْتُ الْحَكَمَ يَقُولُ كَانَ عَلْقَمَةُ صَلَّى خَمْسًا ‏.‏ 33