Sahih Bukhari
Obligatory Charity Tax (Zakat)
Volume: 002 / Book Number: 024 / Hadith Number: 538
Narrated Abu Said Al-Khudri :
Allah's Apostle 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."