Sunan at-Tirmithiy كتاب الأحكام باب ما جاء فى القاضى يصيب ويخطئ
The Messenger of God, peace and blessings of God be upon him, said, "If a judge gives a decision, exerting himself in juristic deduction, and reaches the correct ruling, he has double the reward. And if he [similarly] gives a decision, reaching an incorrect ruling, he has a single reward." (1) Footnotes: (1) He is rewarded for his integrity in exerting himself in juristic deduction, and is not held liable for reaching an incorrect ruling. Click on ḥadīth to read more