The minister said, “There is unanimous agreement that one may not sell what he neither possesses nor owns and then go out to purchase it for the buyer; such a transaction is null and void.”

As for the subject-matter of a sale, several conditions must be met:

1. It must be something whose use is, in itself, lawful. Accordingly, it is invalid to sell anything from which benefit is prohibited—such as wine, swine, instruments of amusement, or carrion—because the Prophet ﷺ declared, “Allah has forbidden the sale of carrion, wine, and idols,” a report agreed upon. In another wording recorded by Abū Dāwūd: “He forbade wine and its price, carrion and its price, and swine and its price.” Likewise, it is impermissible to sell oils that are najis (ritually impure) or that have become najis, for the Messenger of Allah ﷺ said, “When Allah prohibits a thing, He prohibits its price.” In the agreed-upon ḥadīth it was asked: “What about the fat of a carcass? People coat their ships with it, grease hides with it, and use it for lamps.” He replied, “No. It is unlawful.”

2. Both the price and the item sold must be deliverable; if delivery is impossible, the item is treated as non-existent and its sale is invalid. Hence the sale of a runaway slave, a stray camel, a bird in flight, or stolen property by anyone other than the thief—or by someone unable to recover it from the thief—is not valid.