The Messenger in his temples collected offerings from the believers regularly at temple meetings. Charity was never accepted from hypocrites; nor was any type of donation pursued from the open enemy. The Messenger stated plainly to give all that you are able to give to help the Messenger complete his mission.
Zakat is the third pillar of Islam. It is an obligatory act of charity; it is traditionally given once a year. If you are an adult Muslim of sound mind and have possessed a minimum amount of wealth of 3 ounces of gold or 21 ounces of silver (as of 03/01/2023 this is $5,500 USD for gold or $442 USD for silver) and held this wealth for one lunar year than you are required to give 2.5% of your wealth to a cause of your choice that is in accord with the cause of Allah Who Came in the Person of Master Fard Muhammad.
In simple terms, Zakat is calculated as 2.5% percent of your net worth payable minimum once a year.