Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) led us in prayer and fell short or added in it. We said: O Messenger of Allah, has something new occurred in the prayer? He said: "What is that?" We said: You (peace and blessings be upon him) led us in prayer in such and such a way. So he (peace and blessings be upon him) faced the qiblah and performed two prostrations, then gave the salam.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9799