Chapter 57: One-fifth of Booty to the Cause of Allah (Khumus)
Narrated Abu Musa Al-Ash 'ari: 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 (ﷺ) said, "He who fights so that Allah' s Word
(i. e. Islam) should be superior, fights for Allah' s Cause."
Sahih al-Bukhari 3126