he forbade the practice because it harms the seller, who would be letting his goods go for less than the going rate and thus be cheated. The Prophet ﷺ therefore granted that seller the right of annulment. Does this right apply in every case, or only when he has actually been cheated? The scholars hold two opinions—both narrated from Aḥmad. The stronger view is that the right of annulment exists only when the seller has been cheated; the second, which is the apparent position of al-Shāfiʿī, is that it exists unconditionally. Another group of scholars maintained that the prohibition was meant to protect the buyer, for if an intermediary intercepts the seller, purchases the goods, and then resells them, the buyer is the one who suffers.
In short, the Prophet ﷺ prohibited a form of buying and selling that is otherwise lawful until the seller knows the prevailing price—that is, the fair market value—and the buyer knows the quality of the merchandise. The advocate of unsound analogy argues: “The buyer is free to purchase wherever he wishes, for he has already bought from the seller,” just as he claims that a desert-dweller may appoint a town-dweller as his agent. The Lawgiver, however, considered the public good. When a supplier does not know the market price, he is ignorant of the fair value, and the buyer is taking advantage of him. For this reason Mālik and Aḥmad extended the same ruling to every mustarsil—someone who does not haggle—and to anyone ignorant of the item’s value; such a person is like those caravan traders who do not know the price. It follows that one must not sell to these people except at the known rate, the fair market value, even if they are not compelled to buy from that particular seller. Their ignorance of the price, or their complete reliance on the seller without bargaining, places them at a disadvantage. A valid sale requires genuine consent, and consent depends on knowledge. Someone unaware that he has been cheated may or may not truly consent; once he learns of the overcharge and is still content, there is no problem, but if he objects to a fair price, his displeasure is disregarded.
For the same reason the Lawgiver affirmed the right of annulment for anyone who discovers a hidden defect or deception. The default rule in sales is validity and that what lies beneath should match what appears on the surface. When a purchase is made on that basis, the buyer’s consent is presumed to rest upon it. If the commodity later proves to contain fraud or a defect, this is as though it had been described one way and turned out otherwise; the buyer may accept it, or he may refuse. If he is content, the sale stands; if not, he may rescind it. In the Two Ṣaḥīḥs it is related from Ḥakīm ibn Ḥizām that the Prophet ﷺ said, “The two contracting parties…"