Musnad Ahmad 28:42

Yahya 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 (the Prophet) 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.