The factors that are prepared for work: like the land, they are not subject to zakat, except if they are for trade, then they are subject to zakat like trade goods; for Ali - may Allah be pleased with him - said - peace be upon him -: "There is nothing due on the workers," in Sahih Ibn Khuzaymah 4: 20, and Sunan Abu Dawood 2: 99. See: Umda al-Ri'ayah 1: 275.