Musnad Ahmad 28:599

Yahya ibn Hammad narrated to us, Abu 'Awanah informed us, from al-A'mash, 'Uthman ibn Qays narrated to us, from Abu Harb al-Dayli, who said: I heard 'Abdullah ibn 'Amr ibn al-'As saying: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The sky has not shaded, and the earth has not carried, a man more truthful in speech than Abu Dharr."