Complete Commentary on the Whole Bible, by Matthew Henry, at sacred-texts.com
(Deu 9:1-6) The Israelites not to think their success came by their own worthiness.
(v. 7-29) Moses reminds the Israelites of their rebellions.
Moses represents the strength of the enemies they were now to encounter. This was to drive them to God, and engage their hope in him. He assures them of victory, by the presence of God with them. He cautions them not to have the least thought of their own righteousness, as if that procured this favour at God's hand. In Christ we have both righteousness and strength; in Him we must glory, not in ourselves, nor in any sufficiency of our own. It is for the wickedness of these nations that God drives them out. All whom God rejects, are rejected for their own wickedness; but none whom he accepts are accepted for their own righteousness. Thus boasting is for ever done away: see Eph 2:9, Eph 2:11, Eph 2:12.
That the Israelites might have no pretence to think that God brought them to Canaan for their righteousness, Moses shows what a miracle of mercy it was, that they had not been destroyed in the wilderness. It is good for us often to remember against ourselves, with sorrow and shame, our former sins; that we may see how much we are indebted to free grace, and may humbly own that we never merited any thing but wrath and the curse at God's hand. For so strong is our propensity to pride, that it will creep in under one pretence or another. We are ready to fancy that our righteousness has got for us the special favour of the Lord, though in reality our wickedness is more plain than our weakness. But when the secret history of every man's life shall be brought forth at the day of judgment, all the world will be proved guilty before God. At present, One pleads for us before the mercy-seat, who not only fasted, but died upon the cross for our sins; through whom we may approach, though self-condemned sinners, and beseech for undeserved mercy and for eternal life, as the gift of God in Him. Let us refer all the victory, all the glory, and all the praise, to Him who alone bringeth salvation.