Narrated 'Abdullah: We used to pray behind the Prophet and used to say: "As-Salamu 'Al-Allah. The Prophet said, "Allah himself is AsSalam (Name of Allah), so you should say: 'At-Tahiyatu lil-laihi was- sala-watu wat-taiyibatu, as-sallamu 'Alayka aiyuha-n-nabiyyu wa rahrmatu-l-lahi wa barak-atuhu, As-salamu 'alaina wa 'ala 'ibaldi-l-lahi as-salihin. Ashhadu an la ilaha il-lallah, wa ash-hadu anna Muhammadan 'abduhu wa rasuluhu."'

— Sahih Bukhari, Volume 9, Book 93: Oneness, Uniqueness of Allah (Tawheed), Hadith #478