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 the Zuhr or Asr prayer with five rak'ahs. The people said: O Messenger of Allah, has something been added to the prayer? He said: "No; what is that?" They said: You (peace and blessings be upon him) prayed five rak'ahs. So he (peace and blessings be upon him) turned to face the qiblah and performed two prostrations, then said: "These two prostrations are for whoever among you thinks that he has added or left something out."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9817