Narrated 'Abdullah:When we prayed with the Prophet we used to say, "Peace be on Allah from His slaves and peace be on so and so." The Prophet said, "Don't say As-Salam be on Allah, for He Himself is As-Salam, but say, 'At-tahiyatu lil-lahi was-salawatu wat-taiyibatu. As-salamu 'Alaika aiyuhan-Nabiyu warahmatu-l-lahi wa barakatuhu. As-salamu 'alaina wa 'ala ibadillahis-salihin. (If you say this then it will be for all the slaves in heaven or between heaven and earth). Ashhadu an la-ilaha illallahu wa ashhadu anna Muhammadan 'Abduhu wa Rasuluhu.' Then select the invocation you like best and recite it." (See Hadith No. 794, 795 & 796).