Musnad Ahmad 1077:7

'Abd al-Razzaq narrated to us, Ibn Jurayj narrated to us, he said: And Ibn Shihab said: 'Abd Allah ibn Tha'labah ibn Su'ayr al-'Udhri said: The Messenger of Allah (peace and blessings of Allah be upon him) addressed the people two days before the Fitr [Eid al-Fitr], and he said: "Render a sa' of wheat or grain between two people, or a sa' of dates, or a sa' of barley, upon every free person and slave, and young and old."