وسبب وجوب الزكاة ملك النصاب النامي حقيقة أو حكماً
The cause of zakat is ownership of a qualifying nisab with actual or legally recognized growth capacity.
Nisab is the legally specified threshold, and “growing” includes both literal productive property and categories treated as growth-capable in law. Other required conditions, including the passage of a year where applicable, are not discarded.
Business inventory illustrates property intended for growth, while money may be treated as capable of growth in law. It does not follow that every valuable personal-use object has the same zakat status.