سنن أبي داود

Some companions of Mu'adh ibn Jabal said: When the Messenger of Allah (ﷺ) intended to send Mu'adh ibn Jabal to the Yemen, he asked: How will you judge when the occasion of deciding a case arises?

He replied: I shall judge in accordance with Allah's Book. He asked: (What will you do) if you do not find any guidance in Allah's Book? He replied: (I shall act) in accordance with the Sunnah of the Messenger of Allah (ﷺ).

He asked: (What will you do) if you do not find any guidance in the Sunnah of the Messenger of Allah (ﷺ) and in Allah's Book?

He replied: I shall do my best to form an opinion and I shall spare no effort.

The Messenger of Allah (ﷺ) then patted him on the breast and said: Praise be to Allah Who has helped the messenger of the Messenger of Allah (ﷺ) to find something which pleases the Messenger of Allah.