«مانع يمنع تمام العلة، كهلاك النصاب أثناء الحول»
Another impediment prevents completion of the cause, as where the qualifying nisab is lost during the relevant annual period.
The initial basis exists, but the legally required continuity or completion does not. The author therefore classifies the obstruction at the completion stage.
Not every temporary fluctuation in assets has the same legal result; this example teaches the classification, not every detail of zakat liability.