Sahih Bukhari
One-fifth of Booty to the Cause of Allah (Khumus)
Volume: 004 / Book Number: 053 / Hadith Number: 354
Narrated Aslam:
'Umar said, "Were it not for those Muslims who have not come to existence yet, I would have distributed (the land of) every town I conquer among the fighters as the Prophet distributed the land of Khaibar."