One-fifth of Booty to the Cause of Allah (Khumus)

Bukhari :: Book 4 :: Volume 53 :: Hadith 352

Narrated Abu Huraira:

Allah's Apostle said, "Allah guarantees him who strives in His Cause and whose motivation for going out is nothing but Jihad in His Cause and belief in His Word, that He will admit him into Paradise (if martyred) or bring him back to his dwelling place, whence he has come out, with what he gains of reward and booty."