through the reports of coin minters, money changers and others who have melted down these dirhams and determined their silver content. No material uncertainty therefore remains; indeed, this knowledge is more evident than that obtained through estimation or similar methods. Their sole purpose is to exchange dirhams for dirhams in an amount corresponding to their share, not to obtain additional silver. If they found someone who would mint these dirhams for them in pure silver, without any choice on their part, so that the coins remained in their country, they would do so and pay him his fee. They thus benefit from the pure dirhams they receive without suffering any harm.
Likewise, the owners of the pure dirhams benefit from receiving these dirhams without suffering any harm.
This provides a “third rationale” establishing permissibility: riba was prohibited because it involves taking an excess, which is an injustice that harms the giver. It was therefore prohibited because of the harm it entails. If the exchange is more beneficial to each party than breaking up his dirhams, and each needs what he receives, it serves a benefit that both need. Preventing it would harm them both. The Lawgiver does not prohibit benefits that outweigh the harms and impose the lesser harm instead, as is established by the fundamental principles of Islamic law.
This is comparable to someone receiving a “suftaja” (a remittance arrangement) from a lender: the lender advances him dirhams to be repaid in another town. For example, the lender wishes to transport dirhams to another town, while the borrower has dirhams there but needs dirhams in the lender’s town. He therefore borrows from him in the town where the lender’s dirhams are, and writes