2 Chronicles 20:10
And now, behold, the children of Ammon and Moab and mount Seir, whom thou wouldest not let Israel invade, when they came out of the land of Egypt, but they turned from them, and destroyed them not; And now, behold, the children of Ammon and Moab and mount Seir, whom thou wouldest not let Israel invade, when they came out of the land of Egypt, but they turned from them, and destroyed them not;
The verse is spoken as part of Jehoshaphat's prayer while he stood in the congregation of Judah and Jerusalem in the house of the Lord. It recalls that when Israel came out of Egypt, God did not permit Israel to invade the children of Ammon and Moab and Mount Seir, so Israel turned away from them and destroyed them not but spared them. Jehoshaphat appeals to that past restraint and reminds God that those same peoples are now coming to attack Judah and to cast them out of the possession God gave them to inherit, rewarding that mercy with invasion. The prayer confesses that Judah has no might against the great company coming against it and does not know what to do except to keep its eyes upon God.
For God's people today this means God is their strength and strong tower of defense with all power and limitless resources, so they are not to trust in princes or put fallible human beings in the place of God. In every emergency the battle belongs to God, and apparent impossibilities will only make the victory greater.