So many things in the Old Testament really speak to me. 2 Chronicles 20 is no exception. I actually cried while reading it. No joke.
Moabites, Ammonites, and men from Mt. Seir are marching on Judah unprovoked. They have a vast army, they're on their way, and King Jehoshaphat has no idea what to do. So he does the best thing a man can do when he's at the end of his own wisdom, that is, he called upon the Lord. He pronounced a fast for all of Judah, and he prayed in front of the entire kingdom, pleading for God's help.
I think the key words of his prayer were: "For we have no power to face this vast army that is attacking us. We do not know what to do, but our eyes are upon you."
And through the discernment of a man called Jahaziel, God answered:
"Do not be afraid or discouraged because of this vast army. For the battle is not yours, but God's." He goes on to say, "You will not have to fight this battle."
Now, we know from previous parts of the Old Testament that the Lord is a Warrior, the Lord is our Banner, and the rest of the war-like attributes of YHWH. Judah might not have known that they literally would have to fight NO battle. They might have thought that Jehovah would be fighting with and for them and that they would succeed. Not so.
Not one from the kingdom of Judah perished. Not one had to swing a sword or loose an arrow. At the vanguard of the army of Judah, King Jehoshaphat placed men worshipping and praising God, presumably instead of his strongest fighters, and as they crested the hill to the battlefield...
...no army waited for them there! Well, that's incorrect...there was an army, but every Moabite, Ammonite and Meunite warrior that had marched out against Judah lay dead on the ground. They had ambushed and scuffled with each other, and by the time Judah got there, none had survived. If the Lord can slay an entire army of men without any help from His people, how much more so our little problems and worries!
"Do not be discouraged. Do not be afraid. The Lord is with you."
What more needs to be said?