It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that he said: "We used to be with the Messenger of Allah (peace and blessings be upon him) (in prayer) and we did not know anything (about the tashahhud), so the Messenger of Allah (peace and blessings be upon him) said: 'Say in every sitting (of the prayer): At-tahiyyatu lillahi was-salawatu wat-tayyibatu lillah, salamun alayka ayyuha an-nabiyyu, as-salamu alayna wa ala ibadillahis-salihin, ashhadu an la ilaha illallahu wa ashhadu anna Muhammadan abduhu wa rasuluh (All verbal acts of worship are for Allah, and all bodily and financial acts of worship are also for Allah alone. Peace be upon you, O Prophet (peace and blessings be upon him). Peace be upon us and upon the righteous servants of Allah. I bear witness that there is no god worthy of worship except Allah, and I bear witness that Muhammad (peace and blessings be upon him) is His servant and His Messenger).'"
Imam al-Tabarani (may Allah have mercy on him) said: "No one narrated this hadith from Abu Ishaq (may Allah have mercy on him), from Alqamah (may Allah have mercy on him), except Zayd bin Abi Unaysah (may Allah have mercy on him), and no one narrated it from Zayd bin Abi Unaysah (may Allah have mercy on him) except Amr bin al-Harith (may Allah have mercy on him), and Ibn Wahb (may Allah have mercy on him) is alone in narrating it."