The ruling on currency exchange with the deferral of part of the amount

Question:
The questioner says: I asked a person to exchange five hundred riyals for me, but he said, "I do not have anything but four hundred; the remaining hundred, I will give it to you later." What is the ruling on this transaction? Is it a sale, or is it merely an exchange?

Answer:
This is an exchange, and this transaction is not permissible. If he does not have enough money to complete the exchange, he should exchange the rest with his neighbors or with the people of the market. Yes, or tell him, "I will give you your balance; I will give you your balance tomorrow or soon." However, if you give him part of it and he takes your money and gives you part of it in exchange, that is not permissible. They must not separate while there is something between them. The Prophet (peace and blessings be upon him) said, "They must not separate while there is something between them."