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."  

قَالَ أَعْرَابِيٌّ لِلنَّبِيِّ ﷺ: 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۔»