Abu Dawud said: On this subject this is the soundest tradition, that is, the tradition of Ibn Buraidah: Judges are of three types.
In-book : Book 25, Hadith 3
English translation : Book 24, Hadith 3566
25. The Office of the Judge (Kitab Al-Aqdiyah)
باب الرَّجُلِ يَتَبَوَّأُ لِبَوْلِهِ