We never “get beyond the gospel” in our Christian life to something more “advanced.” The gospel is not the first “step” in a “stairway” of truths, rather, it is more like the “hub” in a “wheel” of truth. The gospel is not just the A-B-C’s of Christianity, but it is the A to Z of Christianity. The gospel is not just the minimum required doctrine necessary to enter the kingdom, but the way we make all progress in the kingdom.
We are not justified by the gospel and then sanctified by obedience but the gospel is the way we grow (Gal. 3:1-3) and are renewed (Col 1:6). It is the solution to each problem, the key to each closed door, the power through every barrier (Rom. 1:16-17).
It is very common in the church to think as follows: “The gospel is for non-Christians. One needs it to be saved. But once saved, you grow through hard work and obedience.” But Colossians 1:6 shows that this is a mistake. Both confession and “hard work” that is not arising from and “in line” with the gospel will not sanctify you — it will strangle you. All our problems come from a failure to apply the gospel. Thus when Paul left the Ephesians he committed them “to the word of his grace, which can build you up” (Acts 20:32).
The main problem, then, in the Christian life is that we have not thought out the deep implication of the gospel, we have not “used” the gospel in and on all parts of our life. Richard Lovelace says that most people’s problems are just a failure to be oriented to the gospel — a failure to grasp and believe it through and through. Luther says (on Gal. 2:14), “The truth of the Gospel is the principle article of all Christian doctrine… Most necessary is it that we know this article well, teach it to others, and beat it into their heads continually.”