Explanation of the author's statement: "And if one of them drops it, the option of the other remains, and if its duration has passed, the sale becomes binding."

The Shaykh :"And if one of them drops it, the option of the other remains" means that if the contract is completed and one of them says, "I have dropped my option," or the other asks him to drop his option and he does so, the option of his partner remains. This is indicated by the saying of the Prophet (peace and blessings be upon him) in the hadith of 'Abdullah ibn 'Umar This indicates that it is valid for one of them to drop the option for his partner.
"And if its duration has passed, the sale becomes binding" If the author (may Allah have mercy on him) had said, "And if they separate, the sale becomes binding," that would have been better, as it aligns with the hadith, due to his saying So the best, meaning the preferable, phrasing is to say "And if they separate, the sale becomes binding". His statement that the sale becomes binding means that it becomes binding and neither of them can annul it except for a cause. This issue is a matter of scholarly consensus, and the basis for this consensus is the saying of the Prophet (peace and blessings be upon him and his family) The binding nature here is from both sides, meaning it is binding from the side of the buyer and from the side of the seller. By this, we know that the sale is one of the binding contracts, because contracts are of three types: binding from both sides, permissible from both sides, and binding from one side only. Binding from both sides is like the sale and the lease. Permissible from both sides is like agency. Permissible from one side is like a pledge; it is permissible for the pledgee to annul it, but binding for the pledgor, because the pledgor cannot annul the pledge, whereas the pledgee has the right to annul it.