Zakat is a determined right (haqq mu''ayyan) which Allah has obligated in specific kinds of wealth, when they reach a specific threshold (nisab), after the passage of one lunar year (hawl), to be given to specific categories of recipients (those mentioned in at-Tawbah 9:60). It is not voluntary charity — it is a pillar of Islam and a portion that the poor have a right to in the wealth of the rich ("And in their wealth was a known right for the beggar and the deprived." al-Ma''arij 70:24–25). The obligated wealth is of four types: (1) gold, silver, and currency — at the rate of 2.5%; the nisab is the value of 85g of gold or 595g of silver (and we adopt the silver nisab as it is more beneficial to the poor today). (2) Crops and fruits at harvest — 10% if rain-watered, 5% if irrigated by effort, with a nisab of 5 awsuq (~653 kg). (3) Livestock — camels, cattle, and sheep — at the detailed rates in the Sunnah, when they reach their respective nisabs and are grazing for most of the year. (4) Trade goods — calculated at the end of the hawl on their current market value at 2.5%. Personal use items (one''s home, car, furniture, working tools, clothing) are not subject to zakat.