Musnad Ahmad 28:204

Yahya ibn Sa'id narrated to us, from Ibn 'Ajlan, from 'Amr ibn Shu'ayb, from his father, from his grandfather, that the Prophet, peace and blessings of Allah be upon him, saw a gold ring on one of his companions, so he turned away from him. He (the companion) threw it away and took a ring of iron. He said: "This is worse; this is the adornment of the people of the Fire." So he threw it away and took a ring of silver, and he (the Prophet) remained silent regarding it.