Sahih Muslim
The Book of Zakat (Kitab Al-Zakat)
Book Number: 005 / Hadith Number: 2154
Sad b. Abu Sarh heard Abu Sa'id al-Khudri as saying: We used to take out as the Zakat of Fitr one sa' of grain, or one sa' of barley or one sa' of dates, or one sa' of cheese or one sa' of raisins.