Sayyiduna Thawban (may Allah be pleased with him) narrates: the Prophet (peace and blessings be upon him) passed by one of his Companions who had a copper ring on his hand. He (peace and blessings be upon him) said: "What is this?" He said: It is for weakness (an ailment called al-wahinah). He (peace and blessings be upon him) said: "Take it off."
Hadith Referenceالمعجم الكبير للطبراني / باب الثاء / 1426