The reason for prohibiting the exchange of paper riyals for nickel riyals at a different rate

Question:
Our brother the Shaykh says: You mentioned in the chapter on riba (usury or interest) that it is not permissible to exchange, for example, three new riyals for one riyal. I would like to mention the reason for this distinction?

Answer:
The reason is that this is a single type. The Prophet (peace and blessings be upon him)—the Prophet (peace and blessings be upon him), as it came in the hadith, if the type is the same, he says . The type here is the same because it is a Saudi riyal; this is a Saudi nickel riyal, and this is a Saudi paper riyal, so it is a riyal of one type. So what is the basis for preferring one over the other? This is not permissible because the type is the same. The Messenger (peace and blessings be upon him) says if they differ. Here, the type did not differ; it is all Saudi riyals, so an increase is not permissible. This is the reason for the prohibition.