Conditions for selling gold for gold

This is a message sent to the program from Muhammad Abdul Karim al-Bani from Riyadh. In his message, he says: What is the ruling on buying gold with gold, weight for weight, where one is new and the other is old, knowing that the old gold is cleaned of stones, dye, and fabric, and the fee for the new gold’s craftsmanship is paid?
Answer: It is not permissible to sell old gold for new gold with an increase equal to the cost of craftsmanship. Rather, it is obligatory that this be sold for that, weight for weight, like for like, equal in every respect. If the owner of the new gold is not satisfied with that, let him buy it for a separate price. He buys the old gold for a separate price and hands it over to its owner, and then the owner buys the new gold for a separate price. As for selling this for that with an increase, it is not permissible, even if the increase is equal to the cost of craftsmanship. This is based on the saying of the Prophet (peace and blessings be upon him): . What some people do is a mistake and is not permissible: selling gold for gold with an increase equal to the cost of craftsmanship or for any other reason. This is not permissible, even if one is poor quality and the other is good, or if one is old and the other is new. The Messenger (peace and blessings be upon him) did not distinguish between them. However, the way to the permissible is to sell the old gold for a separate price to whoever he wishes. Once he receives the price, he buys new gold with it and adds from his own funds whatever he wants to spend on buying the new gold. In this way, everyone is safe from riba (usury or interest).
The presenter: In reality, what happens now is that the shop owner tells him the value of his old gold, and then says: Deduct it from the value of the new gold and pay me the difference.
Answer: This is not permissible, nor is it acceptable. The sale must be separate. Gold for gold, absolutely, must be equal in every respect, even if one is higher in value than the other due to its newness, the quality of its gold, or something similar. It must be equal.
The questioner: In terms of weight?
The Shaykh: In terms of weight. Otherwise, let him sell this one separately and that one separately. Also, another condition: It is not permissible to sell him the old gold for a separate price on the condition that he buys the new gold from him. It is not a condition. He sells it to him, even if he does not buy from him. He sells him the old gold for a separate price and receives it from him, whether he buys the new gold from him or not. After that, he is free; if he wishes, he buys from this person, and if he wishes, he buys from someone else. Yes.
The presenter: You have done well. May Allah bless you.