Once Messenger of Allah ﷺ offered five rakʿat in the Zuhr prayer, and somebody asked him whether there was some increase in the prayer. Messenger of Allah ﷺ said, "What is that?" He said, "You have offered five rakʿat." So Messenger of Allah ﷺ performed two prostrations of Sahu after Taslim.  

أَنَّ رَسُولَ اللَّهِ ﷺ صَلَّى الظُّهْرَ خَمْسًا فَقِيلَ لَهُ أَزِيدَ فِي الصَّلاَةِ فَقَالَ وَمَا ذَاكَ قَالَ صَلَّيْتَ خَمْسًا فَسَجَدَ سَجْدَتَيْنِ بَعْدَ مَا سَلَّمَ