Abu Rashid said: I asked Sayyiduna Salman al-Farisi (may Allah be pleased with him) about the tashahhud, and he said: "I will teach you just as the Messenger of Allah (peace and blessings be upon him) taught me. The Messenger of Allah (peace and blessings be upon him) taught me the tashahhud letter by letter: All verbal, physical and financial acts of worship are for Allah alone. Peace be upon you, O Prophet, and the mercy of Allah and His blessings. Peace be upon us and upon the righteous servants of Allah. I bear witness that there is no god worthy of worship except Allah, alone, without any partner, and I bear witness that Muhammad (peace and blessings be upon him) is His servant and Messenger."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6146