Chapter on Currency Exchange (ṣarf)
Ṣarf is a sale in which both counter-values are of the category of money. Thus, if silver is exchanged for silver or gold for gold, the transaction is valid only when the amounts are equal, even if the coins differ in quality or workmanship, and both sums must be taken into possession before the parties disperse.
When gold is exchanged for silver, inequality of amount is permitted, but mutual hand-to-hand transfer is still obligatory; if the parties separate before each of them has taken possession of his due, the contract is void.
It is impermissible to dispose of the proceeds of a ṣarf deal before actually taking possession of them.
Gold may be sold for silver on the basis of estimation (mujāzafa), without exact weighing.
Someone who sells an ornamented sword for 100 dirhams, the ornament alone being worth 50 dirhams, and then pays 50 dirhams of the price, concludes a valid sale; the amount received is deemed payment for the silver ornament, even if this is not explicitly stated. The same applies if he says, “Take these fifty as part of the price for both the sword and its ornament.” Should full possession not be completed before they separate, the contract is void with regard to both the ornament and the sword whenever the ornament cannot be removed without damage; but if it can be detached without harm, the sale remains valid for the sword and is void for the ornament.
If a silver vessel is sold and the parties separate after only part of the price has been received, the contract is void for the portion not yet received and valid for what has been taken; the vessel becomes shared between seller and buyer in proportion to what has been paid. If part of the vessel is later found to belong to someone else, the buyer may either keep the remainder for its corresponding share of the price or return it entirely.
If a piece of uncoined silver is sold and part of it turns out to be owned by another, the buyer must accept what remains for its share of the price and has no right of rescission.
Whoever sells two dirhams and a dinar for two dinars and one dirham has effected a valid sale, each kind being offset against its counterpart.
Likewise, if eleven dirhams are sold for ten dirhams and a dinar, the sale is valid: the ten dirhams are matched by ten of the same, and the dinar is exchanged for one dirham.
It is also permissible to sell two sound dirhams together with one deficient (ghalla) dirham for a single dirham.