https://abukhadeejah.com/ahmad-ibn-hanbal-usul-sunnah-holding-fast-to-way-of-companions-p1/
Part 1: Holding fast to what the Companions of Allah’s Messenger (salallāhu ‘alaihi wassallam) were upon: Imām Ahmad bin Hanbal’s Usūl As-Sunnah (The Foundations of the Sunnah) with the explanation of Shaikh An-Najmi.