change in price, and we hold that this is a salam contract—an advance payment for future delivery—then, if he returns the principal immediately, or its equivalent, this is what is required.

But if he delays repayment until delivery under the salam contract falls due, then seeks to return an amount equivalent to the principal, this is not truly equivalent to it. Requiring delivery of the stipulated commodity according to its value when the advance was made would therefore be closer to justice. For they mutually agreed that these dirhams would purchase a quantity of that commodity, not something else, but they did not agree upon the quantity. Referring them to a fair valuation is therefore what legal analogy requires, since receipt of the price precedes receipt of the goods.

Likewise, if someone purchases goods without fixing their price, and we hold that the sale is invalid, then, if neither the goods themselves nor their equivalent can be returned, their value must be repaid according to the price prevailing when possession was taken. Just as we require here the value of the goods received, there we require the value of the dirhams received.

An exact parallel is where the goods sold are measured by volume or weight, their price has not been fixed, and payment is deferred for a year. When payment falls due, if he returns wheat, for example, it is not equivalent to the wheat originally received, because its value differs. Paying the value of the goods as assessed when possession was taken, with payment deferred until the time for receiving the price, is therefore more in keeping with justice. This applies equally to the price and the goods sold.

The underlying principle is that whatever comes closer to what the two parties contracted for and mutually agreed upon has a stronger claim to being due than what they neither contracted for nor mutually agreed upon, and that