which is why the author, may Allah have mercy on him, clarified that immediate settlement and taking possession are stipulated.
If someone were to say: “The hadith mentions nothing but taking possession, and the Messenger’s words are undoubtedly more eloquent than the author’s words,” we would reply: The author’s words contain nothing beyond further clarification; they stand in relation to the hadith as an explanation. The Prophet’s words are understood according to what is customary, and what is customary is that when two parties take possession in a sale, the sale is immediate. For what sense would there be in saying, “I have bought from you one kilogram of gold for one kilogram of gold; keep this kilogram with you as a deposit for a month, then, after that, take possession of it for yourself”? This is an unusual scenario—or perhaps one that does not occur at all. The Prophet ﷺ spoke only of matters that are established, familiar, and prevalent.
The principle, then, is: “When a commodity sold by measure is exchanged for the same type, two things are required: equality and taking possession before the parties separate.”
After the author, may Allah have mercy on him, explained the criterion for determining what forms of ribā are prohibited, he explained the means by which equality is established. For when a ribā-bearing commodity is sold for the same type, immediate settlement and taking possession are required. So by what means is possession established? And by what means do we determine equality?
He explained this in his statement: “A commodity sold by measure may only be sold for the same type by measure, and a commodity sold by weight may only be sold for the same type by weight.” Accordingly, equality in measured commodities is determined by measure, and equality in weighed commodities by weight. Thus, based on what the author stated, a further qualification is added to equality: it must be equality according to the legally prescribed standard—by measure in what is measured, and by weight in what is weighed. The difference between them is that a measured commodity is assessed