Abdullah bin Umar (may Allah be pleased with them both) says that the Messenger of Allah (peace and blessings be upon him) prescribed sadaqat al-fitr of Ramadan upon the people: "A sa' of dates or a sa' of barley, upon every slave and free person, male and female, among the Muslims."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7694