Chapter on Transactions (Buyu')

Trade and commerce are permitted in Islam — indeed, the Prophet Muhammad (peace be upon him) was himself a merchant before prophethood, and many of his Companions were successful traders. However, Islamic commercial law establishes firm principles to ensure that transactions are just, transparent, and free from exploitation. Ibn Abi Zayd al-Qayrawani presents the Maliki school's conditions for valid sale contracts and the various forms of prohibited commercial dealings.

The conditions for a valid sale (bay') in the Maliki school are: the seller and buyer must be legally competent (sane, adult, or a minor with guardian authorization); the offer (ijab) and acceptance (qabul) must match and be expressed in the same contractual session; the subject of the sale must exist, be owned by the seller, be deliverable, and be precisely known to both parties; and the price must be known. The Maliki school permits oral, written, and — for small everyday transactions — conventional conduct (mu'atah) as valid modes of contracting.

The prohibition of riba (usury/interest) is absolute in the Quran and Sunnah. The Maliki school distinguishes two types: riba al-fadl (exchange of the same commodity in unequal quantities) and riba al-nasi'ah (deferred exchange with a premium). The six Ribawi commodities identified in the foundational hadith are: gold, silver, wheat, barley, dates, and salt. Exchange of these commodities must be spot (yad bi-yad) and equal in weight or measure for the same commodity. Gold may be exchanged for silver at any rate, but the exchange must be immediate — not deferred.

The Maliki school prohibits several specific commercial forms that involve gharar (excessive uncertainty) or elements of speculation. Among these: selling the unborn young of livestock (habal al-habalah), selling fish in the water or birds in the air, selling crops before they are established on the stalk, a sale with an unknown price (bay' al-majhul), and a sale contingent on an uncertain future event. These prohibitions protect both parties from entering transactions with unjust outcomes.

The Maliki school permits deferred sale (bay' mu'ajjal) — selling goods at a higher price in exchange for deferred payment — provided the price and duration are clearly specified. This is distinguished from riba because the increment is for deferral of delivery of an asset, not for lending money. Bay' al-salam (advance payment for future delivery) is also permissible under specific conditions: the advance price is paid in full at the time of contract, the goods are precisely described, the delivery date is fixed, and the goods are commonly available at the time of delivery.