Musnad Ahmad 27:958

Abu Salamah narrated to us, Malik informed us, from Abdullah ibn Dinar, from Abdullah ibn Umar, that the Messenger of Allah (peace and blessings of Allah be upon him) used to wear a ring of gold. Then the Messenger of Allah (peace and blessings of Allah be upon him) stood up and cast it away, and said, "I will never wear it." He said: So the people cast away their rings.