It wasnarrated from Abu Musa Al-Ash'ari:
"The Messenger of Allah (ﷺ)addressed us and explained the Sunnah for us, and he taught us ourprayer. He said: 'When you perform prayer, and you are sitting, letthe 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 lailaha illallah wa ashhadu anna Muhammadan 'abduhu wa Rasuluhu (Allcompliments, good words and prayers are due to Allah; peace be uponyou, O Prophet, and the mercy of Allah and His blessings; peace beupon us and upon the righteous slaves of Allah. I bear witness thatnone has the right to be worshipped but Allah and I bear witness thatMuhammad is His slave and Messenger). Seven phrases which are thegreeting of the prayer.'"
English reference: Vol. 1, Book 5, Hadith 901
Arabic reference: Book 5, Hadith 954