Musnad Ahmad 937:142

Bahz narrated to us, Shu'bah narrated to us, he said: Wasil al-Ahdab informed me, he said: I heard al-Ma'rur ibn Suwayd say: I met Abu Dharr at al-Rabadhah, and he was wearing a garment, and his servant was wearing a garment. Then he mentioned its meaning.