—whether the sample he receives belongs to the same class, genus, or variety yet is higher or lower in quality than what was first stipulated—provided this takes place only when the delivery date arrives. If anything of the sort is done before that date, it is invalid.

According to Mālik, it is permissible at maturity to receive barley in place of wheat or sult, wheat in place of barley or sult, and sult (a husk-less type of barley) in place of wheat or barley, because in his view the three constitute a single category. One may therefore take any of them for the others, but only in exactly the same measure—no more and no less. Should this substitution occur before the term falls due, it is impermissible. Likewise, if one receives, in barley or sult, more than the measure of wheat that was owed, or in wheat less than the measure of barley that was owed, none of it is valid.

It is allowed to take part of the wheat owed as barley and part of it as wheat or sult, provided the wheat delivered is of the same or of an inferior grade to what had been specified. If the wheat that accompanies the barley or sult is of a higher grade than what was stipulated, the exchange is invalid, and it is not lawful to take possession of any of it before its term.

If the genera and descriptions differ, none of one item may be taken for another—neither at the due date, nor before it, nor after it—such as taking dates for wheat or raisins for dates, and the like.

When the two sides dispute over the agreed description, experts are consulted; the buyer must accept the minimum that still bears that description, unless the contract had explicitly required the very finest grade. If such an upper limit was stipulated and can be objectively ascertained, the decision is in his favor; otherwise, he is entitled only to the best quality available at that time. Some scholars nonetheless frowned upon stipulating an extreme degree of quality in any commodity.