What is the ruling on dealing with a check if the price of the commodity increases with it but decreases with cash?

There is no harm in selling an item for a deferred price higher than its spot price, provided both parties agree and the transaction is finalized. A personal, uncertified check is a deferred check. It is permissible to use it to purchase goods such as furniture and clothing. However, it is not permissible to use it to purchase gold, silver, or currencies, due to the requirement of immediate possession (spot exchange) for these items.

As for a bank-certified check or a cashier's check, they are considered equivalent to immediate possession. It is permissible to use them to purchase gold, silver, and currencies, unless there is an emergency situation where liquidity does not cover the check, in which case it becomes a deferred payment.

The resolution of the Islamic Fiqh Academy and Sharia Standards has stipulated the permissibility of purchasing gold and silver with certified and cashier's checks, with the condition of immediate possession at the time of the transaction.