Ibn 'Abbas said concerning Sadaqatul-Fitr. "A Sa' of wheat, or a Sa' of dates, or Sa of barley, or a Sa' of rye." (Sahih Mawquf)
Sunan an-Nasa'i Book 23, Hadith 75
← Previous Hadith "Give Zakah of your fast." The people looked at one another, so he said: "Whoever is here from the people of Al-Madinah, get up and teach your brothers, for they do lnot know that this Zakah was enjoined by the Messenger of Allah upon every male and female, free and slave, a Sa' of barley or dates, or half a Sa' of wheat. "So they got up. (Da'if) Hisham contradicted him, he said: "From Muhammad bin Sirin."

Sunan an-Nasa'i Book 23, Hadith 74 Next Hadith → I heard Ibn 'Abbas deliver a Khutbah from your Minbar - meaning the Minbar in Al-Basrah - saying: 'Sadaqatul Fitr is a Sa' of food." (Sahih) Abu 'Abdur-Rahman (An-Nasa'i) said: This is the most reliable of the three.

Sunan an-Nasa'i Book 23, Hadith 76