Sahih Muslim
The Book of Zakat (Kitab Al-Zakat)
Book Number: 005 / Hadith Number: 2149
Ibn Umar said that Allah's Messenger (way peace be upon him) prescribed the payment of Zakat-ul-Fitr (on breaking the fast) of Ramadan for people, for every freeman, or slave, male and female among the Muslims-one sa' of dried dates, or one sa' of barley.