Sahih Bukhari
One-fifth of Booty to the Cause of Allah (Khumus)
Volume: 004 / Book Number: 053 / Hadith Number: 329
Narrated Aisha:
Allah's Apostle died, and there was nothing in my house that a living being could eat, except some barley Lying on a shelf. So, I ate of it for a long period and measured it, and (after a short period) it was consumed.