This hadeeth comes under the following chapter: THE REWARD OF THE JUDGE WHEN HE TRIES TO ARRIVE AT A DECISION, WHETHER THAT DECISION IS CORRECT OR INCORRECT
'Amr b. al-'As reported that he heard Allaah's Messenger (sallAllaahu alayhi wa sallam) 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.