And you have seen all that the LORD your God has done to all these nations because of you, for the LORD your God is He who has been fighting for you.
Joshua ends his tenure as the leader of Israel by reminding the nation that they have seen God’s work with their own eyes. Israel itself stood witness.
This same principle applies to Christians. It is not that we have seen God cast nations out of the land in front of us or seen Him defeat physical armies, but that we have all seen His power in our own lives. We have seen Him deliver us from bondage to sin and make us free indeed. We have seen Him give us victory over temptations and deliver us through trials and times of testing. Some have even seen the miraculous. Believers stand witness to the greatness of our God.
The reminder that Joshua includes with that of Israel standing witness to God’s work is that the work is God’s. The temptation to Israel would be to think that their own hands had delivered the Promised Land to them; that somehow their own prowess in battle had secured their victory. Joshua goes on to remind them of the impossibility of Israel having secured their own victory.
The same is true for the Christian. The work is God’s. It is He Who is at work in us both to will and to work His good pleasure. It is He Who began a good work in us and is faithful to complete it. We none of us are saved by our own works so that none of us has any reason to boast in anything but the greatness of our God.
And that is the application. I have seen God’s greatness in my own life. I stand witness to His might and His ability to do what He has promised and more. He delivered me from an anger so intense that I thought it would consume me whole. He has preserved my life multiple times though by all human reckoning I should have died. I also stand witness against myself when I get it into my head that “I can do this.” I never have before. Why should now be any different? Any success I have ever enjoyed in any endeavor undertaken for God—faithfulness, obedience, ministry of any and every kind—has been because God did the work. I need to recognize that and become more reliant on Him. Knowing the greatness of God should result in me relying more and more on Him.