Sayyiduna Abu Musa al-Ash'ari (may Allah be pleased with him) and Sayyiduna Mu'adh bin Jabal (may Allah be pleased with him) narrate: The Prophet (peace and blessings be upon him) sent the two of them to Yemen and ordered them both to teach the people their religion. He (peace and blessings be upon him) said: "You are to collect zakah only from these four kinds of produce: barley, wheat, raisins and dates."
Al-Tabarani recorded it in al-Mu'jam al-Kabir; its narrators are the narrators of the Sahih.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الزكاة / 4399