The buyer requests the item from the merchant, so the merchant buys it from someone else and sells it to him

Question:
He says: Honorable Shaykh, may Allah grant you success. A buyer comes to me, and the item is not in my possession, but I am known for selling it. I tell him, “I will buy it from the market.” So I go and buy it for one hundred riyals, then I inform him that it is for one hundred and twenty. If he accepts, I buy it for him and give it to him. Is my action permissible?

Answer:
There is a distinction here. If you told him, “Wait until I buy the item and bring it to you,” then once you have brought it, you have the choice: if you wish, you buy it, and if you wish, you leave it. There is nothing wrong with that. But if you said, “No, I will buy it,” on the condition that you will not let it go, meaning that you will take it, then this is not permissible, because this is selling what you do not own. Yes.