English Translation
Narrated Abu Musa Al-Ashari: A bedouin asked the Prophet, "A man may fight for the sake of booty, and another may fight so that he may be mentioned by the people, and a third may fight to show his position (i.e. bravery); which of these regarded as fighting in Allah's Cause?" The Prophet said, "He who fights so that Allah's Word (i.e. Islam) should be superior, fights for Allah's Cause."
This hadith is from Sahih al-Bukhari, the most rigorously authenticated collection in Islamic scholarship. No editorial opinion is added.