Asim al-Ahwal says: I saw the cup of the Prophet (peace and blessings be upon him) with Sayyiduna Anas bin Malik (may Allah be pleased with him). It had broken, and he had joined it with a silver wire. Asim says: That cup was very fine and was made of pure tamarisk wood. Sayyiduna Anas (may Allah be pleased with him) says: I gave the Messenger of Allah (peace and blessings be upon him) water to drink in this cup many times.
(b) Ibn Sirin (may Allah have mercy on him) says: There was an iron ring on this cup. Anas (may Allah be pleased with him) intended to put a ring of gold or silver in its place, but Abu Talhah (may Allah be pleased with him) said to him: Do not change what the Messenger of Allah (peace and blessings be upon him) made; leave it as it is.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 116