Imam Zain al-Abidin, may Allah have mercy on him, narrates from his father (Sayyiduna Imam Husayn, may Allah be pleased with him) that Sayyiduna Ali, may Allah be pleased with him, reported: Some Bedouins came to the service of the Noble Prophet, peace and blessings be upon him, and they asked: "Is the payment of Sadaqat al-Fitr obligatory upon us?" The Noble Prophet, peace and blessings be upon him, replied: "It is obligatory upon every young and old, free and slave Muslim; it is one sa’ of dates, barley, or raisins."
Hadith Referenceسنن الدارقطني / كتاب زكاة الفطر / 2068