Fighting for the Cause of Allah (Jihaad)
Bukhari :: Book 4 :: Volume 52 :: Hadith 59
Narrated Abu Huraira:
Allah's Apostle said, "By Him in Whose Hands my soul is! Whoever is wounded in Allah's Cause....and Allah knows well who gets wounded in His Cause....will come on the Day of Resurrection with his wound having the color of blood but the scent of musk."