Chapter 49: The Book of the Etiquette of Judges
It was narrated that Abu Hurairah said: "The Messenger of Allah [SAW] said: 'If a judge passes judgment and strives to reach the right conclusion and gets it right, he will have two rewards; if he strives to reach the right conclusion but gets it wrong, he will still have one reward."
Sunan an-Nasa'i 5381