the goods subject to the salam contract be available both at the time the contract is concluded and at the time delivery falls due. This is the view of Abu Hanifah, may Allah have mercy on him, but there is no evidence for it.
If the goods are unavailable when delivery falls due but are available elsewhere, the apparent meaning of the author’s words is that the contract is invalid, because of the hardship involved in obtaining them from another location.
His statement, “If it, or part of it, becomes unavailable, he may wait, or rescind the whole contract or part of it, and take the payment itself if it remains extant, or its equivalent,” means that if he entered into a salam contract with a due date at which the goods were expected to be available, but they subsequently became unavailable—either because the crops were struck by a calamity and he was unable to deliver them, or because soldiers came upon them and took them—then we say to the purchaser: you have the choice. If you wish, you may rescind the contract and recover the payment; and if you wish, you may leave the contract in force until the seller is able to deliver it to you. This is why the author, may Allah have mercy on him, says, “or rescind the whole contract or part of it, and take the payment itself if it remains extant.” An example of the payment itself being extant is where he paid dirhams to the seller in the salam contract.
Does he have the right to rescind part of the contract? The author says: yes, because whoever has the right to rescind the whole contract has the right to rescind part of it, since the part is included within the whole. For example, he pays him one hundred dirhams in advance for fifty sa‘ of wheat, due in Jumada II. Then Jumada II arrives, and the crops have been struck by blights that destroyed them. We say to the purchaser: you have the choice. If you wish, you may rescind the entire contract; and if you wish, you may rescind part of it, and we will give you the corresponding portion of the payment. So if he says, “I entered into the salam contract for fifty, and I…”