جامع الترمذي

Some men who were companions of Mu'adh narrated from Mu'adh that the Messenger of Allah (ﷺ) sent Mu'adh to Yemen, so he (ﷺ) said: "How will you judge?" He said: "I will judge according to what is in Allah's Book." He said: "If it is not in Allah's Book ?" He said: "Then with the Sunnah of the Messenger of Allah (ﷺ)." He said: "If it is not in the Sunnah of Messenger of Allah (ﷺ)?" He said: "I will give in my view." He said: "All praise is due to Allah, the One Who made the messenger of the Messenger of Allah (ﷺ) suitable."