nor—even that it be simply recorded in writing suffices (1)(2).
If a sale is joined to some other contract within a single transaction, the contract is valid—except when the other contract is kitābah, the slave-manumission agreement.
It is forbidden, once clear consent has been given, to sell over a Muslim’s sale, to purchase over his purchase, or to make a bid over his bid.
Whoever sells a ribā-liable commodity may not, before taking possession of its price, substitute it for something that may not lawfully be sold against it on credit (3).
Likewise, he may not buy back what he sold for anything other than its original price before receiving that price in cash, and the converse is also prohibited (4).
The exchange is, however, permissible when the substitute is of a different genus, or after he has taken possession of the price, or once the commodity’s attributes have changed; it is also permissible if the repurchase is from someone other than the original buyer—even if that person is his own father (5) or son.
Section
[Conditions in a Sale]
It is valid (6) to stipulate deferred payment, or to require a specified pledge or guarantor (7) for that payment, or that the slave be literate,