What is the ruling on returning an item exchanged for currency if the value of the received currency fluctuates?
Chapter on Riba (Usury) and Exchange (Sarf)
Al-Mughni
Book of Sales
Primary text
If the ruling is that return is permissible 'on the same day' (Sarf Yawmihi), it means the return is valid only if the value of the currency received by the seller has not decreased relative to its value on the day of the exchange. If the value of the currency decreases, the apparent position of Ahmad and Al-Khiraqi is that the seller cannot demand the return of the item because the sold item has become defective while in the buyer's possession due to the diminished value of the return consideration.
Supporting text
If the value of the received currency has increased, the return is not prevented, as this increase is not considered a defect. The correct position is that price fluctuation does not prevent return, just as it does not constitute a loss for which one is liable in wrongful seizure (Ghasb), nor does it prevent the return of a defective loan item. If the price fluctuation were considered a defect, the apparent position of the Madhhab is that if the item acquired by the buyer develops a new defect, and subsequently an old defect is discovered, the buyer may return the item, return the value of the newly incurred defect (Arsh al-'Ayb al-hadith), and reclaim the original purchase price.