716 - Issue: He said: (If the defect was extraneous to it, of a different nature, then the currency exchange involving it is invalid.)

This means if one of them finds what he received to be adulterated with a substance of a different nature, it must be examined. If the currency exchange was for a specific item (ayn bi-ayn), it is invalid, as we have previously stated. If it was not for a specific item (ghayr ayn) and he became aware of this during the session, and he returned it and took its substitute, then the currency exchange is valid; because it is the very item upon which the contract was concluded. If they separated before he returned it, the currency exchange is likewise invalid; because they separated before the taking possession of what was contracted upon, and he did not take possession of what serves as a valid substitute for what was contracted upon. This is the manifest view of al-Khiraqi’s statement. It was narrated from Ahmad that if he takes the substitute during the session of the return, it does not become void, just as if the defect were of the same nature. This applies when the purchaser of the defective item was not aware of its defect; but if he was aware of its defect and purchased it as such, and the defect was of the same nature, it is permissible and he has no option, nor is there a substitute. If it was of a different nature, and the currency exchange was gold for gold or silver for its like, then the currency exchange is invalid because it violates equality (tamathul), unless he sells gold or silver that is adulterated for its like in adulteration, such as selling a minted dinar for its like, while knowing the equality of their adulteration, and we have mentioned that the apparent view is its permissibility. If he sells adulterated [currency] for non-adulterated [currency], it is not permissible, unless the adulterant has value, in which case it is analogized to the issue of the 'mudd of ajwah' (a measure of dates). If the currency exchange involved two types, such as gold for silver, it is based on the [validity of] spending adulterated currency.

Section: Regarding spending adulterated currency, there are two narrations. The most apparent of them is permissibility. Salih narrated from him concerning dirhams called al-Musayyabiyyah, the majority of which is copper except for some silver, and he said: 'If it is something they have agreed upon, like fulus (coins of lower value), and they have reached an agreement regarding them, then I hope there is no harm in it.' The second [narration] is prohibition; Hanbal narrated [a ruling] concerning dirhams in which a mixture and copper are blended, and they are bought and sold with it, that it is not permissible for anyone to trade with them. Every case that falls under the name of adulteration makes buying and selling with it prohibited.