From Sahih Bukhari (Hadith 1459):
Narrated Abu Sa`id Al-Khudri:Allah's Messenger (ﷺ) said, "No Zakat is imposed on less than five Awsuq of dates; no Zakat is imposed on less than five Awaq of silver, and no Zakat is imposed on less than five camels
Reference: Bukhari 1459