91 Give ear, O Israel: today you are to go over Jordan, to take the heritage of nations greater and stronger than yourselves, and towns of great size with walls as high as heaven; 2 A people great and tall, the sons of the Anakim, of whom you have knowledge and of whom it has been said, All are forced to give way before the sons of Anak. 3 Be certain then today that it is the Lord your God who goes over before you like an all-burning fire; he will send destruction on them, crushing them before you; and you will send them in flight, putting an end to them quickly, as the Lord has said. 4 And after the Lord has sent them in flight from before you, say not in your heart, Because of my righteousness the Lord has given me this land; when it is because of their evil-doing that the Lord is driving these nations out before you. 5 Not for your righteousness or because your hearts are upright are you going in to take their land; but because of the evil-doing of these nations the Lord your God is driving them out from before you, and to give effect to his oath to your fathers, Abraham, Isaac, and Jacob.
6 Be certain then that the Lord your God is not giving you this good land as a reward 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.