over it, zakat becomes obligatory—even if you intend to build a house with that money or to buy some other necessity. As long as the sum is cash that has reached or exceeded the nisab, a full lunar year has elapsed, and it is still in your possession, zakat is due on it.
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Disbursing zakat to specific needy persons

Question: I work as a manager in one of a merchant’s stores. His habit is to pay his zakat in the month of Ramadan, but he is frequently out of the country. He therefore leaves the zakat money with me together with a list of those to whom he wishes it to be given, telling me, “If any of the people whose names are on this list comes to you, give him the amount I have set aside for him; if he does not come, give nothing to anyone else.” In practice some of those people never show up, so much of the zakat money remains stored away. What is the ruling on this? May a person specify by name the individuals to whom he will pay his zakat, or should he leave the matter open to any rightful recipients without naming specific persons?

Answer: You are a trustee, and you must carry out the instructions of the zakat payer. The zakat should therefore remain with you, and if one of the beneficiaries named on the list comes, you give him the share allocated to him. For anyone who does not come, you keep his portion and hand it back to the owner of the wealth. It is then up to the one on whom zakat is due to decide what to do with the remainder: if he wishes, he may continue to wait for the designated beneficiary; if he wishes, he may redirect it to other eligible recipients.

That said, zakat should not be kept back for a long time; rather, it should be disbursed promptly. It may only be delayed when necessity requires—such as awaiting a particular needy person, or because a period of need, famine, or widespread hunger is anticipated. In those situations, postponing the payment until the expected circumstances arise is permissible.