Fadala bin Ubaid al-Ansari reported: A necklace having gold and gems in it was brought to Allah's Messenger (ﷺ) in Khaibar and it was one of the spoils of war and was put to sale. Allah's Messenger (ﷺ) said: The gold used in it should be separated, and then Allah's Messenger (ﷺ) further said: (Sell) gold for gold with equal weight.
Related hadith on this topic
Explanation & Benefits
Shaykh Umar Farooq Saeedi
Benefits and Issues:
➊ When gold is exchanged for gold, or silver for silver, it is necessary that the weight be equal and the transaction be immediate (hand to hand).
➋ Otherwise, it will constitute usury (riba).
➌ In the case where gold is mixed with another substance, it should be separated.
➍ In mixed items, the correct weight of gold or silver cannot be determined until they are separated.
➎ After separating, the price of everything attached to the gold or silver will also be determined separately, and there will no longer be any possibility of usury (riba).
Source: Sunan Abu Dawood – Commentary by Shaykh Umar Farooq Saeedi, Page: 3353