Sahih Muslim Book 005, Hadith Number 2139.

Chapter : No Zakat is due from a Muslim or his slave or his horse.

Abu Sa'id al-Khudri reported Allah's Messenger (may peace be upon him) as saying: No Sadaqa is payable on the grains and dates till it (comes to the Weight) of five wasqs, or less than five heads of camels, or less than five uqiyas (of silver).