Purchasing a bedroom that a carpenter builds with his own materials

Question:
Honorable Shaykh, may Allah reward you with truthfulness. A man wishes to purchase a wooden bedroom. If it is agreed with the carpenter that he will receive the bedroom ready-made, does this fall under a forward sale (salam), or does it fall under selling what one does not own, since the carpenter does not own those materials at the time of the contract?

Answer:
This is an exception, which they call an exception. The majority of scholars hold that it is not permissible, because it is selling something that does not exist, which has not yet been specified. Only the Hanafis have permitted it; they call it a contract of exception. For example, let someone build a building for you, undertake its construction and all the work, and deliver the profits to you. This is the exception. The majority hold that this is not permissible because it is selling something that does not exist. However, if you negotiate with him so that he builds the building or the room for you, and the materials are yours while he only provides the labor, this is permissible and there is no harm in it. You provide the materials for him, he does the work, and you pay him his wage. This is fine. But if he is the one who pays for the materials, then this is not permissible. Yes.