'Abdullah (b. Mas'ud) reported:

The Messenger of Allah (ﷺ) said five rak'ahs of the noon prayer and when he completed the prayer, It was said to him: Has there been (commanded) an addition In prayer? He said: What is it? They said: You have said five rak'ahs, so he performed two prostrations.

حَدَّثَنَا عُبَيْدُ اللَّهِ بْنُ مُعَاذٍ الْعَنْبَرِيُّ، حَدَّثَنَا أَبِي، حَدَّثَنَا شُعْبَةُ، عَنِ الْحَكَمِ، عَنْ إِبْرَاهِيمَ، عَنْ عَلْقَمَةَ، عَنْ عَبْدِ اللَّهِ، أَنَّ النَّبِيَّ صلى الله عليه وسلم صَلَّى الظُّهْرَ خَمْسًا فَلَمَّا سَلَّمَ قِيلَ لَهُ أَزِيدَ فِي الصَّلاَةِ قَالَ ‏

‏ وَمَا ذَاكَ ‏

‏ ‏.‏ قَالُوا صَلَّيْتَ خَمْسًا ‏.‏ فَسَجَدَ سَجْدَتَيْنِ ‏.‏