It is not because of your righteousness or uprightness of heart that you are going in to possess their land, but it is because of their wickedness that the LORD your God is driving out these nations before you, to keep the promise He swore to your fathers, to Abraham, Isaac, and Jacob.
KJV
Not for thy righteousness, or for the uprightness of thine heart, dost thou go to possess their land: but for the wickedness of these nations the LORD thy God doth drive them out from before thee, and that he may perform the word which the LORD sware unto thy fathers, Abraham, Isaac, and Jacob.
ASV
Not for thy righteousness, or for the uprightness of thy heart, dost thou go in to possess their land; but for the wickedness of these nations Jehovah thy God doth drive them out from before thee, and that he may establish the word which Jehovah sware unto thy fathers, to Abraham, to Isaac, and to Jacob.