The Correct Place of Opinion

Al-Awzāʿī reports that Caliph ʿUmar b. ʿAbd Al-ʿAzīz – Allāh have mercy on him – wrote (in his orders):

There is no place for anyone’s opinion [when it comes to] what is in the Book (revelation). The opinion of the imāms (great scholars) is only regarding what the Book did not come down with, and regarding which no Sunnah has passed from the Messenger of Allāh ﷺ. And the opinion of no one is counted in the face of a Sunnah from the Messenger of Allāh ﷺ.

Al-Ājurrī, Al-Sharīʿah #113 et al.