The root of the dispute lies in how they understood the Prophet—may blessings and peace be upon him—when he said, “Only hand-to-hand (illā hāʾa wa hāʾa).” The expression may be applied more narrowly or more broadly.

Whoever judged that the wording still applies so long as the two parties have not yet left the session—meaning the sale may still be called “hand-to-hand”—allowed a brief delay while they remain together. Whoever held that the wording is not valid unless each exchanger takes possession immediately ruled that, if receipt is postponed after the contract even within the same session, the exchange is void. Because of this understanding they unanimously forbade, in ṣarf, any assignment of debt (ḥawāla), surety (ḥamāla), or option of rescission (khiyār), except for a lone report from Abū Thawr permitting an option.

Within the Mālikī school there is further disagreement over a delay forced upon both exchangers, or one of them. Sometimes they treat it like a voluntary delay; at other times they do not, with details that lie outside the scope of this book.

The Fourth Issue

The scholars also differed regarding a person who exchanges dirhams for dinars and then discovers among the dirhams a counterfeit piece and wishes to return it.

Mālik said: the whole exchange is annulled. If the dinars involved are many, one dinar of the exchange is rescinded for a counterfeit dirham and for anything above that up to the value of a dinar. Should the counterfeits exceed a full dinar by one dirham, another dinar is annulled, and so on until the cancellation reaches the value of one dinar. He added: if the party is content to keep the counterfeit dirham, nothing of the exchange is invalidated.

Abū Ḥanīfah said: the exchange is not vitiated by a counterfeit dirham; it may simply be replaced—unless the counterfeits make up one-half or more of the dirhams, in which case, if they are returned, the exchange is void for the portion returned.

Al-Thawrī said: if the counterfeits are returned, the claimant may choose either to replace them or to become a partner, to that extent, in the dinars—that is, in the share belonging to the owner of the dinars.

Aḥmad said: returning counterfeit coins never invalidates the exchange, whether they are few or many. Ibn Wahb, one of Mālik’s followers, likewise allows substitution in ṣarf; his view rests on the principle that a predominance of delay in such exchanges has no legal effect, especially when it concerns only part of the transaction, and this is the sounder position.

From al-Shāfiʿī two opinions are reported concerning whether counterfeit coins nullify the exchange.

Accordingly, the jurists of the various regions hold four distinct views:

1. The exchange is annulled outright once the counterfeits are returned.
2. The exchange stands, but the counterfeits must be replaced.
3. The ruling differs between small and large amounts.
4. The claimant may choose either to replace the counterfeit coins or to share proportionally with his counterpart.

The basis of all these disagreements is whether a predominance of delay in a currency exchange affects its validity; and if it does, whether it does so in small amounts, in large amounts, or in both.

As for an actual deficiency in weight, opinions in the school fluctuate: at one time they said the exchange is valid if the party accepts the shortage and void if he demands replacement, by analogy with counterfeit coins; at another they said the exchange is void even if he consents to the shortage, and this latter view is weak.

They also disagreed if