Musnad Ahmad 31:812

Ya'qub narrated to us, my father narrated to us, from Ibn Ishaq, who said: Muhammad ibn Yahya ibn Habban and Muhammad ibn 'Abd Allah ibn 'Abd al-Rahman ibn Abi Sa'sa'ah—and they were two men from the Ansar, from the Banu Mazin ibn al-Najjar, and they were trustworthy—narrated to me, from Yahya ibn 'Umarah ibn Abi Hasan and 'Abbad ibn Tamim—and they were from their kin and were trustworthy—from Abu Sa'id al-Khudri, who said: I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "There is no Zakat on less than five awaq of silver, and there is no Zakat on less than five camels, and there is no Zakat on less than five awsuq of dates."