2138. An advance payment transaction is one where the buyer buys an abstractly defined commodity by paying immediately, with the understanding that the commodity will be delivered at a later date. Such a transaction is the converse of a transaction of deferred payment.
Hence if the buyer states, “I am giving you this money so that—for example—after six months I acquire the following commodity (which has been abstractly defined),” and the seller responds by saying, “I have accepted,” or if the seller takes possession of the money, and states, “I have sold that commodity (which has been abstractly defined) and I will deliver it after six months,” the transaction will be valid.