Abu Sa'id al-Khudri (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "There is no zakah on less than five camels, nor is there zakah on less than five uqiyah of silver, nor is there zakah on less than five wasq."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7245