Obligatory Charity Tax (Zakat)
Bukhari :: Book 2 :: Volume 24 :: Hadith 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."