Zakat: وَآتُوا الزَّكَاةَ means “Give zakat.” The words themselves do not specify how often it becomes due.
• In the wealth-and-year example, a person owns the required Nisab1, and a year passes over it. The corresponding zakat becomes due.
• When that stated condition recurs, the duty recurs. Paying once fulfils that year's duty, not every future year's duty.
Hajj: In the example of a person on whom Hajj is obligatory, performing it once fulfils the duty. The same command does not make Hajj obligatory every year.
The lesson is to look for what renews a duty. Prayer, the stated zakat example, and Hajj do not all have the same pattern.
1. Nisab: the specified threshold of wealth relevant to zakat.
- Zakat and Hajj: Different Patterns