From Sahih Bukhari (Hadith 2810):
Narrated Abu Musa:A man came to the Prophet (ﷺ) and asked, "A man fights for war booty; another fights for fame and a third fights for showing off; which of them fights in Allah's Cause?" The Prophet (ﷺ) said, "He who fights that Allah's Word (i.e. Islam) should be superior, fights in Allah's Cause
Reference: Bukhari 2810