سنن ابن ماجه

It was narrated from Abu Musa Al-Ash’ari: “The Messenger of Allah (ﷺ) addressed us and explained the Sunnah for us, and he taught us our prayer. He said: ‘When you perform prayer, and you are sitting, let the first thing you say be: At-Tahiyyatut-tayyibatus-salawatu 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 Muhammadan ‘abduhu wa Rasuluhu (All compliments, good words and 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 is His slave and Messenger). Seven phrases which are the greeting of the prayer.’”