Musannaf Ibn Abi Shayba 36:114

Yahya ibn Adam narrated to us, he said: Wuhayb narrated to us, from Abu Ishaq, from Zayd ibn Arqam, that he heard him say: The Messenger of Allah (may Allah bless him and grant him peace) went on nineteen military expeditions. Abu Ishaq said: So I asked Zayd ibn Arqam, "How many did you go on with the Messenger of Allah (may Allah bless him and grant him peace)?" He said: "Seventeen."