Sunan Ibn Majah, Chapter: The Chapters of Establishing the Prayer and the Sunnah Regarding Them

The Messenger of Allah (saw) used to teach us the Tashah-hud as he used to teach us a Surah of the Quran. He used to say: 'At-Tahiyyatul-Mubarakatus salawatut-tayyibatu lillah; As-salamu 'alayka ayyuhan-Nabiyyu wa rahmatullahi wa barakatuhu; as-salamu 'alayna wa 'ala 'ibadillahis-salihin. Ashhadu an la ilaha illallah wa ashhadu anna Muhammad (SAW)an 'abduhu wa Rasuluhu (All blessed compliments and good prayers are due to Allah; peace be upon you, O Prophet, and the mercy of Allah and His blessings; peace be upon us and upon the righteous slaves of Allah. I bear witness that none has the right to be worshipped but Allah and I bear witness that Muhammad (SAW) is His slave and Messenger).'" [Tashahhud] (Sahih)