1)
Who was the Navi?
1.
Rashi citing Seder Olam: It was Michayahu ben Yimlah.
2)
Why did he say "did you see this gigantic assembly"?
1.
Malbim: If one could win naturally, and does not look to Hashem's salvation, Hashem does not do a miracle.
3)
How will the victory prove that He is Hashem?
1.
Malbim: There were so many enemy soldiers that one could not defeat them naturally, only via a miracle.
