Why are we such slow learners? If you have read through the history of Israel in the books of Kings or Chronicles, you will realize a repeated pattern. Some kings of Israel do evil in the sight of the Lord and lead the nation away from God. The result is always catastrophic in the way that God judges their sin and the nation suffers. There are also times when a king will bring reform, and the people will live in peace and grow in trusting the Lord. It is in those times that the nation of Israel is strong, but it is not their own strength.
Among the other nations, Israel was always the minority in the world. They were surrounded by the whole world as they lived as those called by God and separate from the nations. As you read through the history of Israel, it seems that at any given moment there is a nation ready to come against them and exert its power over them. Along the way we are shown that while Israel seems to be the weak among the mighty of the world, they were called to trust in a strength beyond themselves. Mostly, Israel failed miserably. On a few occasions, however, God gave Israel a faithful king who truly believed that Israel's God was mightier than the nations. Asa was one of those kings.
In 2 Chronicles 14 we find the account of Asa who is described as a king who did good and right in the eyes of the Lord. Asa displayed his faith in God by bringing reform to Judah's worship of God. He removed the idolatrous high places and altars and returned to the commands of the Lord and the worship of the one true living God. He also fortified the cities and raised an army from Judah and Benjamin of over 500,000 men (vs. 1-8). Asa's faithfulness was blessed by God and there was peace in the land. That doesn't mean that other nations were not a threat, but that God was the strength of Israel to protect its peace.
Immediately after reading the introductory summary about Asa's reforms, the threat from another nation arrives (vs. 9). Ethiopia is immediately on Judah's doorstep and while Judah has an army of 500,000, Ethiopia has an army of 1,000,000. Surely, we are meant to see the difference in these numbers. Ethiopia has an army twice the size of Judah's. One could look at this difference and say that the strong is coming against the weak. In human terms, we could not possibly see it any other way. Asa must acknowledge that in this situation Judah is weak and relies on a strength beyond itself. That is exactly what Asa does.
2 Chronicles 14:11-12 And Asa cried to the LORD his God, "O LORD, there is none like you to help, between the mighty and the weak. Help us, O LORD our God, for we rely on you, and in your name we have come against this multitude. O LORD, you are our God; let not man prevail against you." 12 So the LORD defeated the Ethiopians before Asa and before Judah, and the Ethiopians fled.
Asa's prayer is simple. They are mighty and we are weak, but we have God. We rely on God. God is mightier than any man or any number of mighty men. That is why the Chronicler does not record that Asa and Judah won the battle, but that the LORD defeated the Ethiopians before them. God alone is our strength. The lesson for all of God's people is clear. If you belong to the Lord, you can hold onto a strength beyond your circumstance.
After the Lord defeated the Ethiopians, a man called Azariah came out to give King Asa some words of encouragement. He encouraged Asa to see that when people seek God, he is found. When God is the Lord, the people live in victory (15:1-6). After saying this, Azariah gives one more profound encouragement. 2 Chronicles 15:7 But you, take courage! Do not let your hands be weak, for your work shall be rewarded."
This encouragement must be taken in context. Azariah is certainly not saying to Asa that he can work out and produce his own strength. He is making one, simple, profound point. Do not stop trusting God for his strength to be with you. Your courage does not come from yourself but from your diligence to continue trusting in God who is your strength. Don't be passive in this, be active - your work shall be rewarded. Surely, Asa is not to boast in his own strength but in the work that God strengthens and blesses. In the Lord, the weak are strong.
1 Corinthians 1:27 But God chose what is foolish in the world to shame the wise; God chose what is weak in the world to shame the strong.