Musnad Ahmed: Hadith 3910

I heard Ibn Mas'ood (رضي الله عنه) say: The Messenger of Allah (ﷺ) taught me the tashahhud - with my hand between his hands - as he would teach me a soorah of the Qur'an. He said: All compliments, prayers and pure words are due to Allah Peace be upon you, O Prophet, and the mercy of Allah and His blessings. Peace be upon us, and on the righteous slaves of Allah. I bear witness that there is no god but Allah, and I bear witness that Muhammad is His slave and Messenger. (That was) when he was still among us; when he passed away we began to say: peace be upon the Prophet (ﷺ).