Musnad Ahmad 937:283

Mu'awiyah ibn 'Amr narrated to us, 'Abdullah ibn Wahb narrated to us, from 'Amr, from Darraj, from Abu al-Muthanna, from Abu Dharr, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said to me: "Six days. Understand, O Abu Dharr, what is said to you." Except that he said: "And do not harbor a trust, and do not judge between two people."