Is it permissible to sell gold for a loan or exchange it for old gold with an additional sum of money, under the pretext that gold has become a commodity bought and sold like any other, and that the currency is paper money and not gold and silver as it was in the time of the Prophet, peace and blessings be upon him?

Know that usury (riba) is forbidden in gold and silver by textual evidence, based on the Prophet's (peace be upon him) saying: "Do not sell gold for gold unless it is like for like, and do not prefer one part over another, and do not sell silver for silver unless it is like for like, and do not prefer one part over another, and do not sell what is absent for what is present." The prohibition of usury in them is established by the aforementioned text, and the reason for the prohibition being their status as currency is an inferred ruling. An inferred ruling cannot invalidate a definite ruling, because the implication of the text is definitive.