Is it permissible to agree on an exchange rate for currency, then pay the amount three hours later?

"Agreeing on a currency exchange rate with delayed possession occurs in two scenarios: The first is a non-binding promise to ascertain the expected price, and the definitive contract is concluded when both currencies are present. There is no harm in this. The second is a binding agreement or a binding promise, where the delivery of one or both counter-values is delayed. This is forbidden usury (riba), because the condition for currency exchange is immediate possession in the same session, as the Messenger of Allah, peace and blessings be upon him, said: 'If it is hand to hand, then there is no harm; but if it is deferred, then it is not permissible.'"