Deuteronomy 29:13
That he may establish thee to day for a people unto himself, and that he may be unto thee a God, as he hath said unto thee, and as he hath sworn unto thy fathers, to Abraham, to Isaac, and to Jacob. That he may establish thee to day for a people unto himself, and that he may be unto thee a God, as he hath said unto thee, and as he hath sworn unto thy fathers, to Abraham, to Isaac, and to Jacob.
God takes Israel to be His own people and gives Himself to be their God, carrying out what He had said and what He had sworn to Abraham, to Isaac, and to Jacob. The covenant He makes is not limited to those standing before Him at the time, but reaches to those who are not present with them. Those bound by it are called to stay faithful to Him and not to turn aside after other gods. Turning away from Him brings down upon them the curses belonging to the covenant.
As Israel entered that covenant, so believers are to renew their covenant with the Lord and put away stubbornness of heart.