The ruling on currency exchange with a remainder left in the debt

Question:
Some people say: O Shaykh, is it permissible in currency exchange, where deferral is not allowed, for some of your money to remain with the merchant, when this merchant does not have any currency to exchange, so you take some of your money and the rest remains as a debt in his obligation?

Answer:
This is not permissible. The two parties must not separate with something remaining between them, as stated in the hadith: The taking of possession must occur in the assembly, and they must not separate without taking possession of some of the price or some of the exchanged currency. It is obligatory to exchange possession in the assembly. Yes.