When does the option (khiyar) of the two contracting parties in a sale terminate?

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The sale contract becomes binding upon the separation of the two contracting parties (Tafarruq al-Badan). There is no disagreement that the contract is binding after separation occurs. The standard for determining separation reverts to the recognized custom and practice of the people, as the Lawgiver attached a ruling to it without explicit definition. If the parties are in a vast open space, such as a large mosque or a desert, separation occurs when one walks away a few steps with his back to the other. Another opinion states separation occurs when one moves far enough away that he cannot hear the usual speech of the other. Imam Ahmad mentioned regarding the separation of bodies that if one takes something and the other takes something, they have separated. Furthermore, the contract becomes binding if one flees from the other, as this constitutes separation by choice, and the binding nature does not depend on mutual consent. Ibn Umar used to separate from his counterpart to finalize the sale. If they remain in the meeting place, place a screen between them, build a partition, sleep, or walk away together without separating, the option (khiyar) remains due to the absence of separation, regardless of the duration. Separation by death also terminates the option because the option cannot be exercised by the deceased, and the option is not inherited. Furthermore, separation through death is considered a greater form of separation than physical separation, causing the option to cease for the survivor as well.