(6) باب بَيَانِ أَجْرِ الْحَاكِمِ إِذَا اجْتَهَدَ فَأَصَابَ أَوْ أَخْطَأَ
'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.
Reference: Sahih Muslim 1716 a
In-book reference: Book 30, Hadith 18
USC-MSA web (English) reference(deprecated numbering scheme): Book 18, Hadith 4261