The Tashah-hud — Sunan Abi Dawud 970

Alqamah took me by the hand and narrated to me that Abdullah ibn Mas'ud took him by the hand and that the Messenger of Allah (ﷺ) took Abdullah by the hand and taught him the tashahhud in prayer, and he mentioned something like the supplication in the hadith of al-A'mash: "When you say this, or when you finish this, then you have indeed completed your prayer; if you wish to stand, then stand, and if you wish to sit, then sit."