It is narrated from Abu Sa'id Khudri (may Allah be pleased with him), he states that the Messenger of Allah (ﷺ) said: "There is no zakat in less than five camels."
Hadith Referenceمسند الإمام الشافعي / كتاب الزكاة / 705
Hadith Takhrijاخرجه البخارى، الزكاة، باب زكاة الورق، رقم : (1447)۔