Ja'far bin Muhammad (may Allah have mercy on him) narrates from his father (may Allah have mercy on him) that the Messenger of Allah (peace and blessings be upon him) "made sadaqat al-fitr obligatory upon every slave and free person, male and female, among those whom you provide for."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7682