Sayyiduna Fadalah bin Ubayd (may Allah be pleased with him) said: Necklaces containing beads and gold were brought to the Prophet (peace and blessings be upon him) while he was at Khaybar; this was spoils of war being sold. The Messenger of Allah (peace and blessings be upon him) gave the order concerning the gold that was in the necklace that it be removed. Then he (peace and blessings be upon him) said: "Sell gold for gold equal in weight."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10550