Musnad Ahmad 27:1400

'Affan narrated to us, 'Abd al-'Aziz ibn Muslim narrated to us, 'Abdullah ibn Dinar narrated to us, from 'Abdullah ibn 'Umar, who said: The Messenger of Allah (peace and blessings of Allah be upon him) took a ring of gold, so the people took rings of gold. Then he stood one day and said: "I used to wear this ring." Then he cast it away, so the people cast away their rings.