What is the ruling on exchanging old gold for new gold?

Question : The questioner asks: What is the ruling on exchanging old gold for new gold, and the difference in the cost of craftsmanship?

Answer : That is, exchanging gold for gold and paying the difference for the craftsmanship. For example, eighty grams for eighty-five grams; this is not permissible. Because the Prophet (peace and blessings be upon him) said: "Gold for gold, equal in amount, hand to hand." Now, if it is eighty grams for eighty grams, that is equal, but if one has good craftsmanship, and the second person pays for the craftsmanship, say one hundred riyals, is this permissible or not? Some scholars said it is permissible, and some said it is not permissible. The view that is closer to the truth is that one should sell his old gold anywhere, and then buy new gold with its price.