Sahih al-Bukhari 4271
Narrated Salama (in another narration):
I fought seven Ghazwat (i.e. battles) along with the Prophet (ﷺ) and 
also fought in nine battles, fought by armies sent by the Prophet (ﷺ) . Once Abu Bakr was our commander 
and another time, Usama was (our commander).
وَقَالَ عُمَرُ بْنُ حَفْصِ بْنِ غِيَاثٍ حَدَّثَنَا أَبِي، عَنْ يَزِيدَ بْنِ أَبِي عُبَيْدٍ، قَالَ سَمِعْتُ سَلَمَةَ، يَقُولُ غَزَوْتُ مَعَ النَّبِيِّ صلى الله عليه وسلم سَبْعَ غَزَوَاتٍ، وَخَرَجْتُ فِيمَا يَبْعَثُ مِنَ الْبَعْثِ تِسْعَ غَزَوَاتٍ، عَلَيْنَا مَرَّةً أَبُو بَكْرٍ، وَمَرَّةً أُسَامَةُ‏.‏