Sahih Muslim 903
صحيح مسلم#903SahihTawus narrated it on the authority of Ibn 'Abbas that he said:The Messenger of Allah (ﷺ) used to teach us tashahhud as he would teach us a Sura of the Qur'an
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih Muslim is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 4:65