Allah's Apostle enjoined the payment of one Sa' of dates or one Sa' of barley as Zakat-ul-Fitr on every Muslim slave or free, male or female, young or old, and he ordered that it be paid before the people went out to offer the 'Id prayer. (One Sa' = 3 Kilograms approx.)
In the life-time of the Prophet we used to give one Sa' of food or one Sa' of dates or one Sa' of barley or one Sa' of Raisins (dried grapes) as Sadaqat-ul-Fitr. And when Muawiya became the Caliph and the wheat was (available in abundance) he said, "I think (observe) that one Mudd (of wheat) equals two Mudds (of any of the above mentioned things).
In the life-time of Allah's Apostle , we used to give one Sa' of food (edible things) as Sadaqat-ul-Fit,r (to the poor). Our food used to be either of barley, raisins (dried grapes), cottage cheese or dates.
Ibn 'Umar said, "The Prophet made incumbent on every male or female, free man or slave, the payment of one Sa' of dates or barley as Sadaqat-ul-Fitr (or said Sadaqa-Ramadan)." The people then substituted half Sa' of wheat for that. Ibn 'Umar used to give dates (as Sadaqat-ulFitr). Once there was scarcity of dates in Medina and Ibn 'Umar gave barley. 'And Ibn 'Umar used to give Sadaqat-ul-Fitr for every young and old person. He even used to give on behalf of my children. Ibn 'Umar used to give Sadaqatul-Fitr to those who had been officially appointed for its collection. People used to give Sadaqat-ul-Fitr (even) a day or two before the 'Id.
Allah's Apostle has made Sadaqatul-Fitr obligatory, (and it was), either one Sa' of barley or one Sa' of dates (and its payment was obligatory) on young and old people, and on free men as well as on slaves.