أَخْبَرَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، وَمُحَمَّدُ بْنُ بَشَّارٍ، - وَاللَّفْظُ لاِبْنِ الْمُثَنَّى - قَالاَ حَدَّثَنَا يَحْيَى، عَنْ شُعْبَةَ، عَنِ الْحَكَمِ، عَنْ إِبْرَاهِيمَ، عَنْ عَلْقَمَةَ، عَنْ عَبْدِ اللَّهِ، قَالَ صَلَّى النَّبِيُّ صلى الله عليه وسلم الظُّهْرَ خَمْسًا فَقِيلَ لَهُ أَزِيدَ فِي الصَّلاَةِ قَالَ ‏"‏ وَمَا ذَاكَ ‏"‏ ‏.‏ قَالُوا صَلَّيْتَ خَمْسًا ‏.‏ فَثَنَى رِجْلَهُ وَسَجَدَ سَجْدَتَيْنِ ‏.‏

It was narrated that 'Abdullah said: "The Prophet(PBUH) prayed Zuhr with five rak'ahs, and it was said to him: 'Has something been added to the prayer?' He said: 'Why are you asking?' They said: 'You prayed five.' So he turned around and prostrated twice." Translation Not Available

Book Ref: Sunan An Nisai Book 13 Hadith 1254
Web Ref:  Sunan An Nisai Vol 2 Book 13 Hadith 1255