Musnad Abu Ya'la al-Mawsili 42:98

Muhammad ibn Bakkar narrated to us, Fulayh ibn Sulayman narrated to us, from ‘Amr ibn Yahya ibn ‘Umarah, from his father, from Abu Sa’id al-Khudri, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "There is no Zakat (charity) on less than five awaq (of silver). There is no Zakat on less than five awsuq (of dates/grains). There is no Zakat on less than five camels (dhuwd)."