In Center Church Timothy Keller writes that there are three ways of responding to God. While ultimately each of us must either follow him or reject him (two responses), Keller observes that there are two ways to reject him.
“You can reject God by rejecting his law and living any way you see fit. And you can also reject God by embracing God’s law so as to earn salvation. The problem is that people in this last group – who reject the gospel in favor of moralism – look as if they are trying to do God’s will” (Keller, Center Church, 63).
As a result, Keller notes that there are three ways to respond to God: Irreligion (blatant rejection), religion (rejecting God’s grace alone in favor of moralism), and gospel (humbly receiving God’s grace).
Keller also observes that it’s much easier to slip from gospel to religion than the other way around. This is in part because outwardly religion/moralism looks so much like gospel – even though it is radically different. It’s a strong temptation because it is such an effective counterfeit.
As I was reading Keller, I kept thinking back to Hebrews. The original readers of Hebrews weren’t primarily being tempted to slip into irreligion, but to slip back into the Jewish religious system. As far as the writer of Hebrews was concerned, falling back into religion was as dangerous as falling into irreligion since both ultimately meant the rejection of Jesus’ all encompassing work. This is why he took such pains to show the inadequacy of the old priestly and sacrificial system (10:1-4).
If the danger for the early Christians was rejecting Jesus by turning back to religion, the solution was to focus on Jesus. When the author of Hebrews famously exhorts his congregation to “run the race… fixing our eyes on Jesus” (12:1,2) he doesn’t just mean looking to Jesus’ example, but in remembering the salvation he bought us through his perfect life and sacrificial death.
The same is true for us. We never “move past” the gospel. It needs to continually energize our lives. Moralism sometimes brings about external change by restraining sin. Only the gospel – and attention to the gospel – can bring about fundamental transformation.
 I would want to qualify the use of “religion” in this book to mean “attempting to earn salvation” as understood in contrast to gospel. Keller doesn’t mean “organized religion” or “religious practice.”
 For more on the continuity/discontinuity between moralism in Hebrews and modern moralism see this recent post.