Hisham bin Urwah narrates from his father that Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) used to teach the people the tashahhud in the prayer while addressing them on the minbar of the Messenger of Allah (peace and blessings be upon him), saying: "When one of you recites the tashahhud, let him recite it like this: 'Bismillahi khayril-asma, at-tahiyyatuz-zakiyatus-salawatut-tayyibatu lillah, as-salamu 'alayka ayyuhan-nabiyyu wa rahmatullahi wa barakatuh, as-salamu 'alayna wa 'ala 'ibadillahis-salihin, ashhadu an la ilaha illallahu wahdahu la sharika lah, wa anna Muhammadan 'abduhu wa rasuluh' (In the name of Allah, which is the best of names. All verbal, physical and financial acts of worship are for Allah. Peace be upon you, O Prophet, and the mercy of Allah and His blessings. Peace be upon us and upon all the righteous servants of Allah. I bear witness that there is no god but Allah, He is alone and has no partner, and I bear witness that Muhammad (peace and blessings be upon him) is His servant and Messenger)." Sayyiduna Umar (may Allah be pleased with him) said: "After (the mention of) the Messenger of Allah (peace and blessings be upon him), send salam upon yourselves, then send salam upon all the righteous servants of Allah."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2831