Sahih al-Bukhari, Book 64, Hadith 305 (In-Book) ⓘ

Narrated Salama (in another narration): I fought seven Ghazwat (i.e. battles) along with the Prophet and also fought in nine battles, fought by armies sent by the Prophet. 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.‏