Musannaf Ibn Abi Shayba 3:619

Abu Usama narrated to us, from Ibn 'Awn, who said: I heard Ibrahim teaching the Tashahhud: "The greetings (at-tahiyyat) are for Allah, and the good things (at-tayyibat), and the prayers (as-salawat). 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."