Compiled by Imam Yahya ibn Sharaf al-Nawawi
وعن عمرو بن العاص رضي الله عنه سمع رسول الله صلى الله عليه وسلم يقول: "إذا حكم الحاكم، فاجتهد، ثم أصاب، فله أجران، وإن حكم واجتهد، فأخطأ، فله أجر" ((متفق عليه)).
I heard the Messenger of Allah (ﷺ) saying, "When a judge utilizes his skill of judgement and comes to a right decision, he will have a double reward, but when he uses his judgement and commits a mistake, he will have a single reward."[Al-Bukhari and Muslim]