Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) says that the Messenger of Allah (peace and blessings be upon him) "made the zakah of Ramadan obligatory: a sa' of dates or a sa' of barley, upon every male and female, free and slave." Then the people regarded half a sa' of wheat as equal to it. Sayyiduna Ibn Umar (may Allah be pleased with them both) used to give dates; one year the people of Madinah found dates scarce, so he gave barley. Sayyiduna Ibn Umar (may Allah be pleased with them both) used to give it when the people sat to receive it, and they used to sit a day or two before Eid al-Fitr. He used to give on behalf of every young and old member of his household, to the extent that he even gave on behalf of the children, that is, he gave on behalf of the sons of Nafi'.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7697
Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) says: "We used to give sadaqat al-fitr as a sa' of dates, or of barley, or of wheat, or of cheese (aqit), or a sa' of raisins."
This is the wording of Yahya bin Yahya's narration. In the narration of Imam al-Shafi'i (may Allah have mercy on him) it is: "a sa' of food, a sa' of barley"; he did not mention the word "or" at this place, and mentioned it after that. Sufyan al-Thawri (may Allah have mercy on him), narrating from Zayd bin Aslam, added these words: "We used to give sadaqat al-fitr in the time of the Prophet (peace and blessings be upon him)," and then he mentioned the rest of the hadith.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7698
Qabisah bin Uqbah (may Allah have mercy on him) says that Sufyan (may Allah have mercy on him) informed us and mentioned this hadith with the same chain and meaning: that even when the Messenger of Allah (peace and blessings be upon him) was present among us, we used to pay sadaqat al-fitr from these kinds (of food).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7699
Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) says that in the time of the Messenger of Allah (peace and blessings be upon him) the people used to give sadaqat al-fitr as a sa' of barley, or a sa' of dates, or a sa' of raisins, or a sa' of hulless barley (sult).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7700