The ruling on taking samples of goods from merchants at a fixed price and selling them in the market at a higher price

Question:
We say: Honorable Shaykh, may Allah grant you success. If a merchant has a quantity of goods and says, “Take a sample from it and display it in the market. It is yours at fifty riyals per piece,” and you go and display these pieces at a higher price, knowing that the rest of the goods are still with the merchant, is this action permissible?

Answer:
It is permissible to trade in what the sale was concluded upon. What the sale was concluded upon is binding, it becomes yours, and you pay the price to the seller. As for what the sale was not concluded upon, no, a new contract is required for the remaining goods of the same type as the goods you purchased. Yes.