Is it forbidden for two sisters to exchange two gold rings of the same karats (light karats) if the concern is only with the appearance and the weight is not precisely observed, knowing that the two rings are close in weight?

The exchange of gold for gold is impermissible except under two conditions: equality in weight and immediate possession (qabḍ) at the contracting session. Therefore, exchanging gold for gold with a difference in weight or with a delay in possession is not permissible. The questioner and her sister erred by not observing the weight of the gold during the exchange. The way out of this is for each of them to sell her ring to the other for money, and then the other buys the ring she desires with money. They must now undo the sale; each should take her ring back from the other, and then they may conduct a new sale with money if they wish, because a usurious transaction is invalid and must be annulled.