Oneness, Uniqueness of Allah (Tawheed)

Bukhari :: Book 9 :: Volume 93 :: Hadith 555

Narrated Abu Huraira:

Allah's Apostle said, "Allah guarantees (the person who carries out Jihad in His Cause and nothing compelled him to go out but Jihad in His Cause and the belief in His Word) that He will either admit him into Paradise (Martyrdom) or return him with reward or booty he has earned to his residence from where he went out."