The sales contract by mutual exchange

It is allowed to perform a sales contract by giving and taking the prices and items being exchanged. This is because the definition of a sale is to exchange something desireable for something desireable. The proof of this is that the words "trade", "buy" and "sell" is used in the Quran simply to mean "exchange" such "buying deviance for guidance" (2,16).

The sales contract by mutual exchange takes effect when one of the parties receives his part of the deal, whether it is a price or a good.