Is Zakat obligatory on all wealth that has reached the nisab and on which a full year has passed, or is it obligatory only on the amount that first had a full year pass on it, even if the wealth increases thereafter?

The nisab is equivalent to 85 grams of pure gold, or 595 grams of pure silver. Zakat becomes obligatory if the wealth reaches the lower of the two nisabs and a full lunar year has passed over it, during which it did not fall below the nisab.

Wealth acquired as business profit is subject to zakat when the hawl (lunar year) of the principal capital is completed. As for wealth acquired through other means, such as salary or inheritance, zakat is due on the acquired amount when a full year passes over it from the time of its possession. It is permissible to pay zakat in advance for wealth on which a full year has not yet passed.