What is the ruling on conditions that are inherent to the contract or serve the parties' interest?

Primary text

Conditions that are inherent to the contract's requirements, such as stipulating immediate handover or the option of the assembly (khiyar al-majlis) and taking possession immediately, are considered non-effecting; their presence is like their absence, providing no legal ruling and not influencing the contract. Conditions related to the mutual interest of the contracting parties, such as stipulating a deferred payment (ajal), the option to rescind (khiyar), mortgage (rahn), guarantee (damin), or specifying a particular quality in the sold item (like craftsmanship or writing), are valid and must be fulfilled. There is no known difference of opinion regarding the validity of these two categories of conditions.