كتاب الجهاد والسير
32  
The Book of Jihad and Expeditions
(49)
Chapter: The number of campaigns of the Prophet (saws)
(49)
باب عَدَدِ غَزَوَاتِ النَّبِيِّ صلى الله عليه وسلم
Sahih Muslim 1815 a

It has been narrated on the authority of Salama who said:

I joined seven military expeditions led by the Messenger of Allah himself (ﷺ), and nine expeditions which he sent out once under Abu Bakr and once under Usama b. Zaid.
حَدَّثَنَا مُحَمَّدُ بْنُ عَبَّادٍ، حَدَّثَنَا حَاتِمٌ، - يَعْنِي ابْنَ إِسْمَاعِيلَ - عَنْ يَزِيدَ، - وَهُوَ ابْنُ أَبِي عُبَيْدٍ قَالَ سَمِعْتُ سَلَمَةَ، يَقُولُ غَزَوْتُ مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم سَبْعَ غَزَوَاتٍ وَخَرَجْتُ فِيمَا يَبْعَثُ مِنَ الْبُعُوثِ تِسْعَ غَزَوَاتٍ مَرَّةً عَلَيْنَا أَبُو بَكْرٍ وَمَرَّةً عَلَيْنَا أُسَامَةُ بْنُ زَيْدٍ ‏.‏
Reference : Sahih Muslim 1815a
In-book reference : Book 32, Hadith 179
USC-MSA web (English) reference : Book 19, Hadith 4469
  (deprecated numbering scheme)