Musannaf Ibn Abi Shayba 13:1820

Abu Bakr narrated to us, he said: Jarir narrated to us, from Mughira, from Ibrahim and al-Sha'bi, they both said: If the polytheists come to you and make you the judge between them, then judge between them with the judgment of the Muslims; do not transgress it to anything else. Or turn away from them and leave them and the people of their religion.