Amr bin Shu'ayb (may Allah have mercy on him) says: It reached me that the Prophet (peace and blessings be upon him) ordered a crier to announce: "Sadaqat al-fitr is due upon every Muslim," and he narrated the full hadith. Ata' (may Allah have mercy on him) says: Two mudds of wheat, or a sa' of dates or of barley, and in this the slave and the free person are equal.
Abd al-Razzaq likewise narrated it from Ibn Jurayj, from Amr, with a broken chain (munqati').
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7727