Hanafis: Zakat is financial worship and legal capacity—including adulthood and sanity—matters to liability, so a minor’s wealth is not liable under this rule.
Al-Shafi‘i: Zakat is a right attaching to wealth, so it can be due on a minor’s or insane person’s property and be paid by the guardian.
The dispute turns on whether the adult’s personal capacity for worship is a condition of liability or whether the financial right remains due on the property itself.