Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) narrated: The Messenger of Allah (peace and blessings be upon him) led us in prayer. When he finished, we said: O Messenger of Allah, has some new ruling come down regarding the prayer? He (peace and blessings be upon him) said: "No, I am only a human being like you; when I forget, remind me." Then he faced the qiblah with them and said the takbir, and they all said the takbir; then he prostrated and they all prostrated; then he said the takbir and prostrated, and they all prostrated; then he gave the salam to his right and to his left.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10153