What is the ruling regarding fulfilling the price of an item if the currency used in the original contract is split?
Chapter on Riba (Usury) and Exchange (Sarf)
Al-Mughni
Book of Sales
Primary text
If an item is purchased for half a Dinar, the buyer is obligated to provide half a split Dinar. If the buyer then purchases another item for another half Dinar, he is obligated to provide another half split Dinar. If the buyer pays a whole Dinar instead of the required split halves, the second contract is voided because it implicitly includes a condition that increases the price of the first contract.
Supporting text
If the payment of the whole Dinar occurred before the first contract became binding, the contract is voided because what invalidates it was present before its completion. If the payment occurred after the parties separated following the binding of the first contract, this does not affect the first contract, and the buyer is only obligated to pay the price agreed upon in the sale.