(4) باب زَكَاةِ الْفِطْرِ عَلَى الْمُسْلِمِينَ مِنَ التَّمْرِ وَالشَّعِيرِ
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.
Reference: Sahih Muslim 984 a
In-book reference: Book 12, Hadith 16
USC-MSA web (English) reference(deprecated numbering scheme): Book 5, Hadith 2149