Is an oath taken regarding an act impossible by custom legally binding?

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An oath concerning an act impossible by custom, such as ascending to heaven, flying, or traversing a great distance in a short time, is legally binding upon the oath-taker. This view is held by Al-Qadi and Abu Al-Khattab because the act is conceivable, which validates the oath. The expiation (kaffarah) becomes immediately due because fulfilling the oath is despaired of, necessitating the expiation immediately, similar to when one swears to divorce his wife and she dies before he can do so.