كتاب الإمارة
33  
The Book on Government
(42)
Chapter: One who fights so that the word of Allah will be supreme is fighting in the cause of Allah
(42)
باب مَنْ قَاتَلَ لِتَكُونَ كَلِمَةُ اللَّهِ هِيَ الْعُلْيَا فَهُوَ فِي سَبِيلِ اللَّهِ ‏‏
Sahih Muslim 1904 c

It has been narrated (through yet another chain of transmitters) on the same authority, i. e. Abu Musa, who said:

We, came to the Messenger of Allah (ﷺ) and said: Messenger of Allah, one of us hho fights to display his valour... (followed by the same words as we have in the previous tradition).
وَحَدَّثَنَاهُ إِسْحَاقُ بْنُ إِبْرَاهِيمَ، أَخْبَرَنَا عِيسَى بْنُ يُونُسَ، حَدَّثَنَا الأَعْمَشُ، عَنْ شَقِيقٍ، عَنْ أَبِي مُوسَى، قَالَ أَتَيْنَا رَسُولَ اللَّهِ صلى الله عليه وسلم فَقُلْنَا يَا رَسُولَ اللَّهِ الرَّجُلُ يُقَاتِلُ مِنَّا شَجَاعَةً ‏.‏ فَذَكَرَ مِثْلَهُ ‏.‏
Reference : Sahih Muslim 1904c
In-book reference : Book 33, Hadith 216
USC-MSA web (English) reference : Book 20, Hadith 4686
  (deprecated numbering scheme)