It is reported that Sufyān b. ‘Uyainah – Allāh have mercy on him – said:
Verily, the Messenger of Allāh ﷺ is the highest standard; things are measured by him: his character, lifestyle and behavior. Whatever agrees with [these] is true and correct, and whatever contradicts [them] is wrong.

Al-Khatīb Al-Baghdādī, Akhlāq Al-Rāwī wa Ādāb Al-Sāmi’ article 8.