Musnad Abu Ya'la al-Mawsili 117:24

Ibrahim ibn al-Hajjaj al-Sami narrated to us, Bashar ibn al-Hakam narrated to us, Thabit al-Bunani narrated to us, from Anas, who said: The Messenger of Allah (may Allah bless him and grant him peace) met Abu Dharr and said: "O Abu Dharr, shall I not guide you to two characteristics that are lighter on the back and heavier in the scale than others?" He said: "Yes, O Messenger of Allah." He said: "You must have good character and long silence. For by the One in whose hand is my soul, the creatures have not adorned themselves with anything like them."