Mukhtasar Bukhari

Sayyiduna Amr bin Al-As (may Allah be pleased with him) heard from the Messenger of Allah (peace and blessings of Allah be upon him), he (peace be upon him) said: "When a ruler exercises ijtihad (independent judgment) in passing a judgment and he is correct, then he has a double reward, and when he exercises ijtihad in passing a judgment and makes a mistake, then he has a single (onefold) reward."