It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) ordered Zakat al-Fitr: a sa' of dates, or a sa' of barley, or two mudds of wheat, upon every town-dweller and desert-dweller, young or old, free or slave.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10683