91 Hear, Israel: you are to pass over the Jordan this day, to go in to dispossess nations greater and mightier than yourself, cities great and fortified up to the sky, 2 a people great and tall, the sons of the Anakim, whom you know, and of whom you have heard say, “Who can stand before the sons of Anak?” 3 Know therefore this day, that Yahweh your God is he who goes over before you as a devouring fire; he will destroy them, and he will bring them down before you: so you shall drive them out, and make them to perish quickly, as Yahweh has spoken to you. 4 Don’t say in your heart, after Yahweh your God has thrust them out from before you, saying, “For my righteousness Yahweh has brought me in to possess this land;” because Yahweh driwes them out before you because of the wickedness of these nations. 5 Not for your righteousness, or for the uprightness of your heart, do you go in to possess their land; but for the wickedness of these nations Yahweh your God does drive them out from before you, and that he may establish the word which Yahweh swore to your fathers, to Abraham, to Isaac, and to Jacob.
6 Know therefore, that Yahweh your God doesn’t give you this good land to possess it for your righteousness; for you are a stiff-necked people.
Matthew Henry's Commentary on Deuteronomy 9:1-6
Commentary on Deuteronomy 9:1-6
(Read Deuteronomy 9:1-6)
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 Ephesians 2:9,11,12.