6 Understand, then, that it is not because of your righteousness that the LORD your God is giving you this good land to possess, for you are a stiff-necked people.

Read Deuteronomy 9:6 Using Other Translations

Understand therefore, that the LORD thy God giveth thee not this good land to possess it for thy righteousness; for thou art a stiffnecked people.
"Know, therefore, that the LORD your God is not giving you this good land to possess because of your righteousness, for you are a stubborn people.
You must recognize that the LORD your God is not giving you this good land because you are good, for you are not—you are a stubborn people.