It was narrated that Ibn 'Abbas (رضي الله عنه) said:

The Messenger of Allah (ﷺ) used to teach us the Tashahhud as he taught us the Qur'an, he used to say: "All blessed compliments and good prayers are due to Allah; peace be upon you, O Prophet, and the mercy of Allah and His blessings; peace be upon us and upon the righteous slaves of Allah, I bear witness that there is no god except Allah and I bear witness that Muhammad is the Messenger of Allah."