He replied:

This hand-to-hand exchange is permissible according to the stronger of the two scholarly opinions. Its permissibility rests on two grounds—indeed, three:

First: This silver contains copper, whereas the other silver is pure, and the silver mixed with copper is less in quantity. Thus, if one hundred dirhams of the former are exchanged for, say, seventy pure dirhams, the silver contained in those hundred dirhams is less than seventy dirhams. If the additional silver is treated as payment for the copper, this is permissible according to one of the two scholarly opinions: that of those who permit the “mudd of Ajwa dates” transaction. This is the position of Abū Hanīfa and of Ahmad according to one of the two reports from him. It is also the position of Mālik and, according to the well-known report, Ahmad, when the item subject to the rules of riba (usury) is incidental to something else. Examples include selling a sheep that produces milk for milk, a house gilded with gold for gold, or a sword adorned with silver for silver or gold, and similar transactions.

As for those who prohibit the “mudd of Ajwa dates” transaction—namely, exchanging a commodity subject to the rules of riba for another of the same kind when both, or either one, are accompanied by something of a different kind—some of them, among the followers of al-Shāfi‘ī and Ahmad, explain their prohibition as follows: when a transaction comprises two different items, the price is apportioned between them according to their respective values. This, however, is a weak rationale.

For when someone sells a share subject to pre-emption together with something not subject to it—such as a slave, a sword, or a garment—if apportionment is impermissible, the co-owner has recourse to the person exercising pre-emption. As for apportioning the price according to value without any need, there is no evidence supporting it.