The Messenger of Allah صلى الله عليه وسلم said: "Judges are of three types, one of whom will go to Paradise and two to Hell. The one who will go to Paradise is a man who knows what is right and gives judgment accordingly; but a man who knows what is right and acts tyrannically in his judgment will go to Hell; and a man who gives judgment for people when he is ignorant will go to Hell."
Sunan Abu-Dawud, Book 24, Number 3566: Narrated Buraydah ibn al-Hasib