Sahih Bukhari
One-fifth of Booty to the Cause of Allah (Khumus)
Volume: 004 / Book Number: 053 / Hadith Number: 362
Narrated Nafi from Ibn Umar:
Allah's Apostle sent a Sariya towards Najd, and Abdullah bin 'Umar was in the Sariya. They gained a great number of camels as war booty. The share of each one of them was twelve or eleven camels, and they were given an extra camel each.