Sahih Bukhari Volume 2, Book 25, Hadith Number 587.
Narated By Nafi’ : 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.