Chapter: Usury (ribā) and Currency Exchange

Both forms of ribā—ribā al-faḍl (surplus usury) and ribā al-nasīʾa (deferred usury)—are unlawful.

Ribā al-faḍl
Therefore, a commodity that is ordinarily sold by volume may not be exchanged for another of its own kind, nor a commodity sold by weight for its own kind, unless the amounts are exactly equal and the exchange is completed hand-to-hand. Nor may something usually sold by volume be traded for its own kind by weight or in an unspecified quantity (1), and the same prohibition applies to an item usually sold by weight: it may not be exchanged for its kind by volume or in bulk without precise measurement.

When the two commodities are of different genera—such as wheat for barley—the sale is permissible whether conducted by volume, by weight, or without specification.

It is invalid to sell meat for a live animal of the same species; to sell grain for its own flour or suwayq (toasted coarse flour); to sell the raw product for the cooked, the pure for the mixed, or the fresh (moist) for the dry—except in the case of ʿarāyā.

Nonetheless, it is valid to sell flour for an equal amount of flour provided their fineness is identical, and bread for bread provided their dryness is the same. One may not sell pitted dates for dates that still contain their pits, nor may a ribā-liable commodity be exchanged for its own kind when something of a different genus is attached to either side, such as trading one mudd of ʿajwah dates together with one dirham for one mudd of ʿajwah dates and one dirham (2), or for two mudds of them.

It is, however, permissible to sell date pits for dates that contain pits, and to sell wool or milk for an animal that possesses wool or produces milk, and the like.