Sahih Muslim 1815
Sahih Muslim · Book 32: The Book of Jihad and Expeditions · The number of campaigns of the Prophet (saws)
وَحَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ ، حَدَّثَنَا حَاتِمٌ ، بِهَذَا الإِسْنَادِ . غَيْرَ أَنَّهُ قَالَ فِي كِلْتَيْهِمَا سَبْعَ غَزَوَاتٍ .
The (foregoing) tradition has also been narrated on the authority of Hatim through the same chain of transmitters with the difference that according to this version both these types of expeditions were seven in number.