The third is mutual exchange by the buyer.

An example of mutual exchange by both parties is where there are, for instance, medicines bearing their stated prices, with a container for payment placed beside them. The buyer comes, puts the price of this medicine into the payment container, and takes the medicine. This is mutual exchange by both parties.

Mutual exchange by the seller is where the buyer says, “Give me bread for this dirham,” and the seller takes a bag of bread and gives it to the buyer. This is mutual exchange by the seller.

Mutual exchange by the buyer is where the seller says, “Take this book for ten,” and the buyer takes it without saying, “I accept,” but gives him ten. Here, the mutual exchange is by the buyer. The seller has specified the price and made the offer, saying, “I have sold you this book for ten,” or, “Take this book for ten.” The buyer then takes it without speaking and gives him the ten. This shows us that transactions are a matter in which there is latitude; they are referred back to what people customarily recognize. All people customarily recognize this mutual exchange as constituting a clear contract.

In summary, a sale contract has two forms: verbal and action-based.

The verbal form consists of the offer and acceptance. The offer is the wording issued by the seller or one acting in his place, and the acceptance is the wording issued by the buyer or one acting in his place. We have already mentioned the conditions of acceptance.

As for the second form, it is the action-based form, namely mutual exchange.

The commentator (1) gave a rationale that we should understand. He said: “Because there is no prescribed form of worship involved …”