It is likewise permissible for the two contracting parties to stipulate that the option be given to one of them only, for the right belongs to them both; therefore, whatever arrangement they mutually approve is valid.

Third: The option due to overreaching (khiyār al-ghabn). When one of the parties is disadvantaged in the sale by an excess that exceeds what people ordinarily tolerate, the wronged party may either uphold the contract or rescind it, in view of the Prophet’s ﷺ words, “There must be neither harm nor reciprocating harm,” and his ﷺ statement, “The property of a Muslim is not lawful except with his willing consent.” Because the victim of overreaching is not truly content, the option exists; but if the disparity is slight and customarily accepted, no option is granted.

Khiyār al-ghabn arises in three situations.

The first is intercepting caravan-riders (talqī al-rukbān), meaning people who are bringing their goods into town. If someone meets them on the way, buys their merchandise, and it later becomes clear that he underpaid them by a large margin, they are granted the option, for the Prophet ﷺ said, “Do not go out to meet incoming goods; whoever meets them and buys from them, then when the owner reaches the market he has the choice.” Narrated by Muslim. Thus the Prophet ﷺ forbade purchasing merchandise outside the market where goods are normally sold, and he ruled that once the seller reaches the marketplace—where prices are known—he may either let the sale stand or annul it.