Musnad Ahmad 26:755

Husayn ibn Ali narrated to us, from al-Hasan ibn al-Hurr, from al-Qasim ibn Mukhaymirah, who said: Alqamah took my hand, and said: Abdullah took my hand, and said: The Messenger of Allah (may Allah bless him and grant him peace) took my hand, and taught me the Tashahhud in prayer: "The greetings (at-tahiyyat) are for Allah, and the prayers (as-salawat) and the good things (at-tayyibat). 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 but Allah, and I bear witness that Muhammad is His servant and His messenger."