Currency exchange with the remainder deferred

Question:
The Shaykh’s case, may Allah inform you, is that a person asked another to exchange fifty Saudi riyals for him, or ten thousand Saudi riyals, which is called breaking the fifty. So the exchanger gave him forty riyals, and said, “The rest, which is ten riyals, I will give you later, because I do not have current exchange available.” What is the ruling on that?

Answer:
This is not permissible. If he gives him fifty, or a hundred, or five hundred and says, “Exchange it for me,” it is not permissible for them to separate with anything outstanding between them. He must have the entire exchange present; he hands over the fifty, or the five hundred, or the hundred, and receives the full exchange in the same session. As for saying, “This part now, and the rest will come to me later,” this is forbidden. This is forbidden because it is riba al-nasi'ah (usury of deferment). Yes.