Musannaf Ibn Abi Shayba 13:3218

Abu Bakr narrated to us, he said: Ya'la ibn 'Ubayd narrated to us, from Muhammad ibn Ishaq, from Jahm ibn Abi Jahm, he said: One who heard 'Abdullah ibn Ja'far narrating to me said that 'Ali would not attend disputes, and he used to say: "Indeed, it has precipices where the Shaytan is present." So he assigned his dispute to 'Aqil. When he grew old and became frail, he transferred it to me. 'Ali used to say: "Whatever is judged for my agent is for me, and whatever is judged against my agent is against me."