“Against those forms of Judaism that saw the law-covenant not only as lex [law] but as a hermeneutical device for interpreting the Old Testament, Paul insists that the Bible’s story line takes precedence and provides the proper hermeneutical key.”
D. A. Carson, “Reflections on Salvation and Justification in the New Testament,” JETS 40 (1997): 585.
There are two ways to read the Bible. We can read it as law or as promise.
If we read the Bible as law, we will find on every page what God is telling us we should do. Even the promises will be conditioned by law. But if we read the Bible as promise, we will find on every page what God is telling us he will do. Even the law will be conditioned by promise.
In Galatians 3 Paul explains which hermeneutic is the correct one. “This is what I mean: the law, which came 430 years afterward, does not annul a covenant previously ratified by God, so as to make the promise void. For if the inheritance comes by the law, it no longer comes by promise; but God gave it to Abraham by a promise” (Galatians 3:17-18).
So, if we want to know whether we should read the Bible through the lens of law or grace, demand or provision, threat or promise — if we want to know how to read the Bible in an apostolic rather than a rabbinic way — we can follow the plot-line of the Bible itself and see which comes first. And in fact, promise comes first, in God’s word to Abram in Genesis 12. Then the law is “added” — significant word, in Galatians 3:19 — the law is added as a sidebar later, in Exodus 20. The hermeneutical category “promise” establishes the larger, wraparound framework for everything else added in along the way.
The deepest message of the Bible is the promises of God to undeserving law-breakers through his grace in Christ. This is not an arbitrary overlay forced onto the biblical text. The Bible presents itself to us this way. The laws and commands and examples and warnings are all there, fulfilled in Christ and revered by us. But they do not provide the hermeneutic with which we make sense of the whole. We can and should understand them as qualified by God’s gracious promise, for all who will bank their hopes on him.
From Ray Ortlund, Jr.'s blog: Christ is Deeper Still