Sahih Muslim | Book 5 | Hadith Number 2151

Narrated by Ibn 'Umar
Ibn 'Umar said that the Apostle of Allah (may peace be upon him) prescribed the Sadaqa of Ramadan (Sadaqat-al-Fitr) one sa' of dates or one sa' of barley for every free man or a slave, male or female, and then the people equalised (one sa' of dates or barley) with half a sa' of wheat.