It is narrated from Sayyiduna Khalid bin Sa'id bin al-As (may Allah be pleased with him) that he came to the Prophet (peace and blessings be upon him) while there was a ring on his hand. The Prophet (peace and blessings be upon him) asked: "What is this ring?" He said: "It is a ring I had made." He (peace and blessings be upon him) said: "Throw it away." So I threw it to him, and it was a ring of iron. Then the Prophet (peace and blessings be upon him) asked: "What is engraved on it?" I said: 'Muhammadun Rasulullah' (Muhammad is the Messenger of Allah). So the Prophet (peace and blessings be upon him) took it and wore it until his death; it was the very ring that used to be on his (peace and blessings be upon him) blessed hand. This hadith has a sahih (authentic) chain, but the two Shaykhs (Bukhari and Muslim) did not record it.