the owner of the fresh dates from the owner of the dried dates the cash value of those fresh dates. The owner of the wheat is likewise entitled to an equivalent measure of his grain from the owner of the standing crop, while the owner of the crop recovers its value. The same principle applies to every sale in which a fresh commodity is bartered for its dried counterpart.
When the genera differ, however, it is permissible to exchange the fresh for the dried provided that delivery is hand-to-hand, and every commodity for which disparity is allowed may likewise be traded in this way. Another form of muzābanah is to sell clarified butter for fresh butter, milk that produces butter for an amount of butter, sweet grape must for grapes, olive oil for olives, or sesame seed for sesame oil; every one of these exchanges is prohibited in all circumstances.
An exception is camel’s milk for butter, which may be sold hand-to-hand because camel milk yields no butter. Conversely, it is not lawful to sell the milk of animals other than camels for clarified butter or for cheese.
Whenever the genera differ, none of these transactions is deemed muzābanah. Hence there is no objection to selling sesame oil for olive oil, olive oil for sesame seed, or olives for sesame oil in whatever proportions the parties choose, so long as delivery is immediate; everything analogous takes the same ruling.
Muzābanah also includes selling a heap of dried dates for dates still on the palm-trees, a heap of raisins for grapes still in the vineyard, or a heap of grain for standing crops that have ripened. Any commodity that is normally sold by measure is, in this context, treated like such heaps.
Likewise, any edible commodity exchanged for another of its own genus—known for unknown, unknown for known, measured for unmeasured, or weighed for unweighed—falls under the same prohibition. Whatever is lawful only when exchanged equal for equal may not be sold in random quantities, nor may a measured amount be traded for an unmeasured one, nor something whose amount is unknown for another whose amount is likewise unknown, or for a known amount of the same genus. None of this is permissible unless it is equal for equal—measure for measure or weight for weight—and hand-to-hand, except for the dispensation established in the Sunnah concerning ʿarāyā.
According to Mālik, selling a known quantity for an unknown quantity also constitutes muzābanah whenever it is not known that one of the two sides is larger.