Sahih Bukhari Volume 9, Book 93, Hadith Number 550.

Narrated By Abu Musa : A man came to the Prophet and said, “A man fights for pride and haughtiness another fights for bravery, and another fights for showing off; which of these (cases) is in Allah’s Cause?” The Prophet said, “The one who fights that Allah’s Word (Islam) should be superior, fights in Allah’s Cause.” (See Hadith No. 65, Vol. 4)