Sahih Bukhari | Volume 2 | Hadith Number 584

Narrated by Abu Sa'id Al-Khudri
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).