Sayyiduna Salamah bin al-Akwa' (may Allah be pleased with him) says: I took part in seven military expeditions with the Prophet (peace and blessings be upon him), and of the armies he (peace and blessings be upon him) dispatched, I took part in seven of those as well. Sometimes the commander over us was Sayyiduna Abu Bakr (may Allah be pleased with him) and sometimes Sayyiduna Usamah bin Zayd (may Allah be pleased with him). In one narration, nine expeditions are mentioned.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 17898