“[The] Lord wraps up the whole covenant of grace in one promise, signifying no less: “I will be your God.” In the covenant, God becomes our God, and we are his people; and thereby all his attributes are ours also.”
-John Owen (Communion with the Triune God; p. 199)
God has made a covenant with humanity. It is a promise to be our God. It is a promise that if He is our God, we will be His people. As His people we will share in His marvelous attributes of holiness, love, mercy, etc. As an added bonus, the covenant is one of grace.
Grace is what separates Christianity from all other worldviews because salvation is not based upon who we are and what we have done or not done, but based upon the person and work of Jesus Christ. All that is required to enter into the covenant of grace is faith in Jesus Christ as revealed in the Bible.
As if entering into the covenant is not great enough, God has arranged it so that we do not have to go searching all over the place for the blessings of the covenant. All the blessings, promises, rewards, and experiences of the covenant can be found in one place – the Person of Jesus Christ. Jesus, the very One who established the covenant and is the Guarantee of the covenant. Or, as John Owen eloquently phrased it:
“[In] whom this covenant and all the promises thereof are ratified, and in whose blood it is confirmed – to wit, in the Lord Christ alone; in him only is God an all-sufficient God to any, and an exceeding great reward. And hence Christ himself is said to “save to the uttermost them that come to God by him” (Heb. 7:25)” (p. 200)