Riyad as-SalihinChapter 18Hadith 1177
Full Sharh — Riyad as-Salihin 1177
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)).
English Translation
'Amr bin 'Al-'As (May Allah be pleased with him) said:: 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."
Source
Riyad as-Salihin(رياض الصالحين)
The Book of Miscellaneous ahadith of Significant Values
Hadith Number
1177