Zakat (Kitab Al-Zakat)
Dawud :: Book 9 : Hadith 1610
Narrated Abdullah ibn Umar:
The people during the lifetime of the Apostle of Allah (peace_be_upon_him) used to bring forth the sadaqah at the end of Ramadan when closing the fast one sa' of barley whose straw is removed, or of raisins. Abdullah said: When Umar (Allah be pleased with him) succeeded, and the wheat became abundant, Umar prescribed half a sa' of wheat instead of all these things.