The first is the Prophet’s statement, peace and blessings be upon him: “Wheat for wheat, equal for equal” (1). Here, equality is established.

The second is that the Prophet, peace and blessings be upon him, permitted the sale of ʿarāyā—fresh dates for an estimated equivalent amount of dried dates (2). An ʿarāyā sale is the exchange of fresh dates for dried dates. Fresh dates are heavier and also swell, whereas dried dates shrink and become lighter. Yet the fresh dates may be converted into dried dates and sold according to their estimated amount. Likewise, if it is weighed, it has effectively been converted back into grain. This view is correct, because equality is attained and there is a need to exchange one for the other, or to convert flour back into grain by weighing it.

This is analogous to what they said regarding dates that have become compacted—that is, dates pressed tightly together such that they cannot be measured by volume: they are assessed by weight, even though they remain an item customarily measured by volume.

If one sells barley in grain form for wheat flour, it is permissible because the two are of different genera. Thus, it is permissible to sell one sāʿ of wheat for two sāʿs of barley.

But if he says, “I will sell you one sāʿ of grain for one sāʿ of flour, treating the extra amount as compensation for the grinding,” this is not permissible, because an increase resulting from manufacture is like an increase resulting from quality. The Prophet, peace and blessings be upon him, prohibited disparity in exchange where quality differs. The evidence is that some fine janīb dates were brought to him, and he asked, “Are all the dates of Khaybar like this?” They replied, “No, Messenger of Allah. Rather, we take one sāʿ for two sāʿs, and two sāʿs for three.” He said, “Do not do so. Sell the mixed dates for dirhams, then buy janīb dates with the dirhams” (3).