Is Zakat waived from a person who apostatizes after the Zakat obligation has been established?
Chapter on Zakat on Debt and Charity
Al-Mughni
Book of Zakat
Primary text
Zakat established upon a Muslim does not lapse due to subsequent apostasy. The basis for this is that Zakat is a right pertaining to wealth, which is not voided by apostasy, analogous to debt. Unlike prayer, which is not required of the apostate because it cannot be validly performed by them, Zakat can be collected by the Imam from the apostate's wealth, similar to collecting it from a Muslim who refuses to pay. If the apostate returns to Islam after the Imam has collected the Zakat, the obligation to pay is lifted, as the collection itself served as the fulfillment, just as it would for a refusing Muslim.
Supporting text
An alternative view suggests that Zakat is indeed waived because it is an act of worship that requires intention (Niyyah), which is absent in the state of disbelief. Another differing view suggests that if the collection is made by someone other than the recognized authority (Imam or their deputy), the Zakat is not settled, as the collector lacks the proper authority. If the apostate attempts to pay Zakat while being an apostate, it is invalid and must be repeated upon returning to Islam.