Section
On ribā (usury) in gold, silver, and foodstuffs: its forms and underlying legal causes
Ribā in exchanges of foodstuffs for foodstuffs, and of gold and silver for gold and silver, takes two forms: ribā in immediate exchanges and ribā in deferred exchanges. When food of a single kind is storable and serves as a staple or an adjunct to staple food, ordinarily forming a mainstay of subsistence, ribā applies in both forms: unequal quantities may not be exchanged even with immediate delivery, nor may the exchange be deferred, whether the quantities are equal or unequal. The same applies to gold exchanged for gold and silver for silver. When two different kinds of such food are exchanged, unequal quantities are permissible with immediate delivery, but deferment is forbidden, just as when gold is exchanged for silver or silver for gold.
Likewise, when storable staple food is exchanged for food that is neither storable nor a staple, or when food that is neither storable nor a staple is exchanged for other such food, ribā applies only through deferment. According to Mālik—may Allah have mercy on him—and his companions, the legal cause prohibiting unequal quantities of a single kind is that the item is an edible, storable staple or an adjunct to staple food. Some add to this description that it must ordinarily form a mainstay of subsistence, though they differ over whether this qualification should be taken into account.
According to al-Shāfiʿī, the legal cause is edibility alone. He therefore prohibited unequal quantities of a single kind of anything eaten or drunk, whether storable or not, and whether sold by measure or weight or neither. He even prohibited unequal exchanges of scammony and Armenian clay.
According to Abū Hanīfa—may Allah have mercy on him—the legal cause is measurement by volume or weight. He therefore did not permit unequal quantities of a single kind of anything sold by weight or measure, whether it is eaten or drunk or neither. He prohibited exchanging one ratl (a unit of weight) of iron for two ratls of iron, whether with immediate delivery or on deferred terms, because iron is sold by weight. He permitted exchanging one date for two dates and one walnut for two walnuts, since these individual quantities cannot be measured by volume.
Saʿīd ibn al-Musayyab held that ribā applies only to gold, silver, or things eaten or drunk that are sold by weight or measure. Thus, according to him, the legal cause of ribā is edibility combined with measurement by volume or weight. A similar position has been related from al-Shāfiʿī—may Allah have mercy on him—and it is also the position of Abū Thawr. Thus, there is no objection, according to Saʿīd ibn al-Musayyab