هلاك النصاب في أثناء الحول
Destruction of the qualifying nisab during the zakat year.
Possessing nisab at a moment is not identical to meeting the full conditions for a completed zakat year. In the classical case discussed, the qualifying property is lost during the year so that the legally required completion of the ground is prevented.
This is not simply late payment of a zakat debt already fully established. The impediment concerns completion of the operative cause. Lesser fluctuations and later reacquisition of qualifying property involve additional rules not settled by this example alone.