Musannaf Ibn Abi Shayba 13:3018

Abu Bakr narrated to us, he said: Ibn Abi Za'idah narrated to us, from 'Awf, from Muhammad, who said: Shurayh used to say to the litigant: "O servant of Allah, by Allah, I am indeed judging in your favor, and I indeed think you are an oppressor, but I do not judge based on conjecture. Rather, I judge based on what is presented to me. And my judgment does not make lawful for you that which is forbidden to you."