The Criterion of the Lawful Sale and Distinguishing It from the Buy-Back Sale

Question:
I bought a commodity with my money and handed him the cash, but I told him: leave it with you so you can sell it to me. Is it permissible for him to buy it, or should I make him my agent to sell it? We ask for details.

Answer:
If you buy the commodity, you must transfer it from the seller's location to another location, and sell it in another location; because the Prophet (peace and blessings be upon him) said: ; because he (peace and blessings be upon him) forbade selling goods where they were bought, until the merchants take possession of them in their dwellings, and he (peace and blessings be upon him) said: , the commodity is transferred from the seller's location to the market, or to your house, or to another location, where another person sells it to you, and you do not leave it with the one from whom you bought it; you transfer it. And if you sell it to him after you have transferred it, there is no harm. And if you sell it to him because he is the one who bought it from you, there is no harm, provided the price is immediate and present. As for if you bought it from him on credit and then sold it to him for less; this is not permissible. This is called: the buy-back sale.
If you bought it, for example, for 100 riyals, and then sold it to him for 80 or 70 in cash, and the deferred debt remains in your liability, this is called: the buy-back sale. This is not permissible. But if you bought it for a present price of 100 riyals, delivered it to him, and then it occurred to you to sell it to him for its price, or less, or more, there is no harm.