Abu Ishaq narrates: The people went out for istisqa' (the prayer for rain), and Sayyiduna Zayd bin Arqam (may Allah be pleased with him) went out among them. I went close to him and asked: How many military expeditions did the Messenger of Allah (peace and blessings be upon him) undertake? He said: "Nineteen expeditions." I asked: In how many expeditions did you take part with him? He said: "Seventeen expeditions." He said: And he led the people in two rak'ahs. Abu al-Walid added in his narration: I asked: What was the first expedition of the Messenger of Allah (peace and blessings be upon him)? He said: "Dhu al-Ushayrah or Dhu al-Usayrah."
Hadith Referenceالمعجم الكبير للطبراني / باب الزاي / 5023