Musnad Ahmad 27:1428

Sulayman ibn Dawud al-Hashimi narrated to us, Isma'il—meaning Ibn Ja'far—narrated to us, Ibn Dinar informed me, from Ibn 'Umar, from the Prophet (may Allah bless him and grant him peace), that he took a ring of gold and wore it. So the people took rings of gold. Then the Prophet (may Allah bless him and grant him peace) stood up and said: "I was wearing this ring, and I will never wear it again." So he cast it away, and the people cast away their rings.