What is the ruling on exchanging used gold for new gold while paying the difference?

The questioner : May Allah reward you, we hope for your blessing. When the news came, we sent it to the sun, and we were in Riyadh and did not separate, we did not eat or drink, and also fasted at night. Is it obligatory for us to make up the fasts or not?

The Shaykh : This was mentioned in the questions.

The questioner : We are in need, may you live long.

The Shaykh : Yes, I spoke about it. Where are the singers? One word, ask, start with the questions and start with the other person's question.

The questioner : May Allah reward you with good.

The Shaykh : Now it is the turn of the evidence.

The questioner : May Allah be pleased with you, the urgent question, the urgent question,

The Shaykh : Fine, fine, write it down. Yes. Praise be to Allah, Lord of the worlds, and may the prayers and peace be upon our Prophet Muhammad, and upon his family and companions. The questioner says: The Messenger of Allah (peace and blessings be upon him) said, meaning: gold for gold, , that he takes used gold, for example, the price of the gram is thirty riyals, and sells the new gold at a price of forty riyals per gram. What is the ruling on this?
The ruling on this is that it is not permissible, meaning it is not permissible to exchange bad gold for good gold and give the difference. This is forbidden and not permissible. What indicates this is what is established in the two Sahihs and others in the story of Bilal (may Allah be pleased with him). He came to the Prophet (peace and blessings be upon him) with good dates and he said to him: "Are you eating the dates of Khaybar like this?" He said: "No, but we buy one sa' of this for two sa' and two sa' for three." The Messenger of Allah (peace and blessings be upon him) said: The Messenger (peace and blessings be upon him) clarified that increasing what requires equality due to a difference in description is the very riba (usury or interest), and that it is not permissible for a person to do it. But the Messenger of Allah (peace and blessings be upon him), as is his custom, guided him to the permissible way and said: The mixed dates are the bad dates mixed from various shapes, This is the way to which our Prophet (peace and blessings be upon him) guided.