Silsilah Sahihah

Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) narrates that the Noble Prophet (peace and blessings be upon him) wrote a letter to the people of Yemen, that is, to Harith bin Abd Kallal and his companions from the Ma'afir and Himyar tribes, stating: "If the land is irrigated by springs or rain, then one-tenth (1/10) of its produce or wealth is due as zakat, and for those (lands) which are watered by buckets (or similar means), one-twentieth (1/20) of the produce is due as zakat."