What is the ruling on buying 18-karat gold, then returning it after two days and getting a full refund, then buying the same gold again with the same refunded amount?

For the exchange of gold for gold, equality in weight and immediate possession (qabd) are stipulated. The majority of jurists prohibit the sale of gold and currency for gold. However, the Hanafis and Shaykh al-Islam Ibn Taymiyyah permit this if the singular usurious item is more than that which has something else with it, or if each of them has something of a different type, provided that the increase corresponds to the other item, such that the extra grams are equivalent to the money paid.