—exalted is He—“Allah has permitted trade” [al-Baqarah: 275] every sale except those excluded by evidence. The proofs of Islamic law have excluded many kinds of sale; all others therefore retain their original permissibility. This is why we said that permissible sales remain permissible unless Islamic law forbids them or a prohibition concerning them has been reported.
Section
Things in people’s possession fall into two categories: those that cannot validly be owned and those that can. There is consensus that whatever cannot validly be owned may not be sold, such as a free person, wine, pigs, monkeys, blood, carrion, and similar things.
Whatever can validly be owned falls into two categories. The first comprises things that cannot validly be sold, either because their condition precludes their sale—such as a runaway slave, a stray camel, goldsmiths’ dust, and similar things—or because Islamic law prohibits their sale, such as endowed property; the meat of sacrificial animals, according to a number of scholars; a copy of the Quran, according to some scholars; and a dog that one is permitted to keep, according to some scholars of our school. The second comprises things that may validly be sold, provided the sale is not conducted in a manner prohibited by Islamic law.
Section
There are many circumstances in which Islamic law prohibits concluding a sale. Some concern the price and the item sold; others concern the circumstances of the contracting parties; and still others concern the circumstances in which the sale takes place.
As for those concerning the price and the item sold, there is agreement that the sale’s validity or invalidity depends on their absence or presence. The conditions include the absence of usury, knowledge of the price and the item sold, and the absence of ignorance and uncertainty concerning them, together with the other conditions required for a valid sale. As for those concerning the circumstances of the contracting parties or the circumstances in which the sale takes place, these involve distinctions and differences of opinion that I shall explain later, if Allah Most High wills.