It is a contract for something described as an obligation, to be delivered at a later date, in exchange for a price received at the session of the contract. It may be concluded using the wording of sale, salam, or salaf …
His statement, “It is a contract for something described as an obligation, to be delivered at a later date, in exchange for a price received at the session of the contract”: a definition must be both inclusive and exclusive; this is what is meant by a technical definition. Thus, one may say that he defined salam, or that he set out the definition of salam; and one may say: “The definition of salam is such-and-such,” or “The technical definition of salam is such-and-such.” A definition must be inclusive of every instance of the thing being defined and exclusive of anything else. If it is not exclusive or not inclusive, then it is not valid.
Let us now consider the definition of salam.
His statement, “a contract for something described”: this excludes a specific identified item. Salam involving a specific item is not valid, because there is no need for salam in such a case. So long as it is present, it may be sold through an ordinary sale without being salam.
An example is a man who has one hundred sāʿs of wheat in sacks. Another man says to him, “I enter into a salam contract with you, paying one hundred riyals for this wheat.” This is not valid, because it is not for something described; rather, it is for a specific identified item. Therefore, it is invalid. Even if they agree that the seller will not deliver this wheat until one year later, it is still invalid and does not constitute salam.
His statement, “as an obligation,” excludes something described yet specifically identified. A thing may be described and identified, but not owed as an obligation. For example, one may say, “I enter into a salam contract with you, paying forty thousand for your car in the garage, whose specifications are such-and-such.” This is a described but specifically identified item, so salam involving it is not valid, because it is like a specific item that is present. Thus, the author stipulated that it must be something described as an obligation.