Hittan bin Abdullah al-Raqashi narrates that Sayyiduna Abu Musa al-Ash'ari (may Allah be pleased with him) led the people in prayer; he then mentioned the complete hadith. In it, he (peace and blessings be upon him) said: "When he sits, the first thing he should say is: 'At-tahiyyatu at-tayyibatu az-zakiyatu lillah, as-salamu 'alayka ayyuha an-Nabiyyu wa rahmatullahi wa barakatuh, as-salamu 'alayna wa 'ala 'ibadillahi as-salihin, ashhadu an la ilaha illallah, wa ashhadu anna Muhammadan 'abduhu wa rasuluh' (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. I bear witness that there is no god but Allah, and I bear witness that Muhammad (peace and blessings be upon him) is the servant of Allah and His Messenger)."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3959