Sahih al-Bukhari 3126
Sahih al-Bukhari · Book 57: One-fifth of Booty to the Cause of Allah (Khumus) · If somebody fights for the sake of boty
Narrated Abu Musa Al-Ash`ari:
حَدَّثَنِي مُحَمَّدُ بْنُ بَشَّارٍ ، حَدَّثَنَا غُنْدَرٌ ، حَدَّثَنَا شُعْبَةُ ، عَنْ عَمْرٍو ، قَالَ سَمِعْتُ أَبَا وَائِلٍ ، قَالَ حَدَّثَنَا أَبُو مُوسَى الأَشْعَرِيُّ ـ رضى الله عنه ـ قَالَ قَالَ أَعْرَابِيٌّ لِلنَّبِيِّ صلى الله عليه وسلم الرَّجُلُ يُقَاتِلُ لِلْمَغْنَمِ، وَالرَّجُلُ يُقَاتِلُ لِيُذْكَرَ، وَيُقَاتِلُ لِيُرَى مَكَانُهُ، مَنْ فِي سَبِيلِ اللَّهِ فَقَالَ " مَنْ قَاتَلَ لِتَكُونَ كَلِمَةُ اللَّهِ هِيَ الْعُلْيَا فَهْوَ فِي سَبِيلِ اللَّهِ " .
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."