Chapter on Riba and Currency Exchange

Riba al-faḍl (incremental usury) is forbidden in every commodity that is sold by measure or by weight when it is exchanged for the same genus, and in such a sale both payment and receipt must be immediate. A measured commodity may not be traded for its own kind except after it has been measured, nor a weighed commodity for its own kind except after it has been weighed, and no part of it may be exchanged for part of it on mere estimation; yet if the two sides belong to different genera the three restrictions are lifted.

A “genus” (jins) is any item that has a distinct name embracing various types, such as barley and the like. The branches of a genus are themselves treated as separate genera: the different kinds of flour, breads, and oils are each a distinct genus, and meat is considered to be of different genera according to the animal from which it comes. The same applies to milk, meat, fat, and liver; each is a separate genus.

It is invalid to sell meat for a living animal of the same genus, though it is valid if the animal is of a different genus. One may not sell grain for its own flour, roasted grain for raw, raw for cooked, the original substance for its juice, the pure for the adulterated, or the moist for the dry. It is, however, permissible to sell flour for flour provided the two are equal in fineness, cooked for cooked, bread for bread when their dryness is equal, juice for juice, and moist for moist.

A ribawī article is not to be sold for its own genus when something of another genus accompanies it on one or both sides.1 Dates without pits may not be exchanged for dates that still contain pits, although pits themselves may be exchanged for dates with pits; likewise, milk and wool may be exchanged for a sheep that possesses both milk and wool.

Reference for measurement is the customary measure of Madinah, and reference for weight is the customary weight of Mecca during the time of the Prophet—may Allah bless him and grant him peace.