Musnad Ahmad 5:713

'Abdullah narrated to us, Muhriz bin 'Awn bin Abi 'Awn narrated to me, Sharik narrated to us, from Simak, from Hanash, from 'Ali, who said: The Messenger of Allah (peace and blessings of Allah be upon him) sent me as a judge. He said: "If two disputing parties come to you, do not judge for one of them until you hear from the other, for it will make the judgment clear to you."