The Office of the Judge (Kitab Al-Aqdiyah)
Dawud :: Book 24 : Hadith 3566
Narrated Buraydah ibn al-Hasib:
The Prophet (peace_be_upon_him) 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.