Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) used to teach us the tashahhud and the sermon just as he would teach us a surah of the Qur'an: from "All verbal, physical and monetary acts of worship are for Allah alone" up to "His servant and Messenger."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9870