Muwatta 688

A long saying of Malik: the agreed practice among us regarding debt is that its owner does not pay zakat on it until he collects it; if he leaves it with its debtor for years and then collects it, only one zakat is due. If he collects part of it that is not subject to zakat, and he has other cash on which zakat is due, he pays zakat on it together with that cash; if he has no other cash, he keeps count of what he collected until, with what he collects afterwards, it reaches the threshold, and then he pays zakat, whether he spent what he collected first or not. Malik argues from the case of goods held for trade for years and sold, where only one zakat is due on their price, since the zakat of anything is paid from it, not from other property. ¹

Belongs to the Muwatta, Book of Zakat. Source: the Muwatta. Mentions Malik ibn Anas. Built on in the chapters on zakat and lunar year (hawl).