Is it valid to stipulate a contractual option after the sale has already become binding?
Chapter on the Option of the Two Parties in Sale
Al-Mughni
Book of Sales
Primary text
If the parties add a stipulation for an option after the contract has become legally binding, it is not effective. This is the position of Al-Shafi'i. The reason is that a binding contract cannot be rendered contingent merely by the agreement of the parties, just as a marriage contract cannot be made contingent in this manner. This differs from the ruling within the session of contracting because, within the session, the contract is still contingent (Ja’iz) and thus capable of modification.
Supporting text
Abu Hanifa and his school hold that it is effective because the parties retain the right to dissolve the contract, thus they can stipulate an option just as they could during the session of contracting.