Narrated Amr bin Al-'Aas that he heard Allâh's Messenger (ﷺ) I saying, If a judge gives a verdict according to the best of his knowledge and his verdict is correct (i.e. agrees with Allâh and His Messenger's verdict), he will receive a double reward, and if he gives a verdict according to the best of his knowledge and his verdict is wrong, (i.e., against that of Allâh and His Messenger ﷺ) even then he will get a reward." [9:450-O.B]