Sahih Muslim Book 4, Hadith 63
The Messenger of Allah (ﷺ) taught me tashahhud taking my hand within his palms, in the same way as he taught me a Sura of the Qur'an, and he narrated it as narrated above.
We were sitting with the Apostle (ﷺ) in prayer, and the rest of the hadith is the same as narrated by Mansur He (also said): After (reciting tashahud) he may choose any prayer.
The Messenger of Allah (ﷺ) used to teach us tashahhud just as he used to teach us a Surah of the Qur'an, and he would say: All services rendered by words, acts of worship, and all good things are due to Allah. Peace be upon you, O Prophet, and Allah's mercy and blessings. Peace be upon us and upon Allah's upright servants. I testify that there is no god but Allah, and I testify that Muhammad is the Messenger of Allah. In the narration of Ibn Rumh (the words are): "As he would teach us the Qur'an."