Chapter 31: The Book of Judicial Decisions
' Amr b. al-' As reported that he heard Allah' s Messenger (ﷺ) as saying: When a judge gives a decision, having tried his best to decide correctly and is right, there are two rewards for him; and if he gave a judgment after having tried his best (to arrive at a correct decision) but erred, there is one reward for him.
Sahih Muslim 1716a