If the excess is greater than that, the exchange of two dinars is rescinded; and whatever exceeds that will always be dealt with on the very same proportional basis. Such is the ruling for a returned amount and for every other issue that may surface in currency exchange.

Some of Mālik’s companions drew further distinctions in this matter: whether the dirhams were exchanged by number or by weight; whether the bad coin was leaden, copper, or adulterated; and whether the fault lay in a shortage of weight or in outright counterfeiting. Ibn ʿAbd al-Ḥakam states in Foundations of Sales: “When someone exchanges dinars for dirhams by weight and then finds among them a coin that is deficient, broken, or so badly worn that it will not pass in the market, he has no right to return it, and no part of the transaction is dissolved on that account. If, however, he discovers copper, lead, or a debased dirham among them, he may return it if he wishes, and only the equivalent of one dinar is deducted from the exchange; its ruling is exactly the same as what I described earlier.”

The scholars of Medina and others hold two opinions on this question. One view is that the coin is simply replaced and nothing of the exchange is reduced; this is the position of al-Layth ibn Saʿd, al-Awzāʿī, and Aḥmad ibn Ḥanbal. The other view is that the exchange is void only with respect to the amount that is returned, while it remains valid for what has already been taken possession of; a number of scholars have adopted this as well.

If one of the two parties has already spent part of the exchanged funds and then finds that what remains is defective, and the other party acknowledges the defect, he must restore the like of what he has spent, matching its specie and weight. The entire exchange is then revoked, and each of them reclaims from the other the very same type of currency he had originally paid.