Martin Luther famously called it the article the church stands or falls by. Justification by grace through faith is that important. The offer of a right standing with God because of absolutely nothing we have done, rather because of absolutely everything that Jesus has freely done for us, and crucially his self sacrificial, substitutionary death on the cross bearing our sins to hell - this is the great foundation of a standing, prevailing church, and a standing, prevailing Christian.
And of course, this is crucial to the gospel we preach, when we call on people to turn from their idols, to serve a living and true God and to wait for his Son from heaven, whom he raised form the dead, Jesus, who rescues us from the wrath that is coming. The offer of being restored to a right relationship with God is utterly free, as free as the grace of Jesus Christ, who loved us and gave himself up for us. We are justified by his blood, it's pure grace, and it gives glorious assurance.
It's possible to undermine that grace and assurance, however, in two ways.
On the one hand, we can dilute the freeness of the offer, by adding our own works to the cross of Jesus Christ as the grounds of justification. This legalistic, merit based righteousness is always attractive to the human heart because it preserves our pride, and evades the scandal of the cross. But it is not the gospel, it is the opposite of the gospel.
On the other hand, we can dilute the freeness of the offer of God's grace in Jesus Christ by preaching sanctification by willpower through works, even thought we preach justification by grace through faith.
Of course, we have to preach sanctification, that is, the ongoing growth in Christlikeness of character - after all, this is the will of God, our sanctification (1 Thess 4.3). The aim of Biblical instruction is love that comes from a pure heart, a good conscience, and sincere faith (1 Tim 1.5). Or another way to put it is to say that we preach for transformation, not just information.
The thing is that it's possible to preach justification by grace through faith, but to preach sanctification by willpower through works. In fact, any time we call on people to change - to repent of their sins, to put off the works of darkness and to cloth themselves with Christ - without explicitly grounding this change in a dynamic of grace, we are doing just that. It is in effect 'Nike' sanctification - just do it, or just stop doing it. Suck it up, be more focused, exercise more self control, engage the spiritual disciplines more, and try harder.
And actually, when you listen carefully, many sermons and Bible studies and pastoral conversations boil down to something like this. They may have more or less wording, but the actual spiritual dynamic at play is the same. Even the appeal to identify - 'God, by his grace, has made you his child, given you a new identity, now live out that identity' - has the same Nike structure.
Preaching sanctification like this can be catastrophic. It can lead to either one of two things. First, for most, they will find that they cannot consistently make the changes called for. They will try and fail, and confess their sins, and for a time, perhaps even decades, that will work - kind of. But after months or years, they will find themselves more and more crushed by the inevitable call to sanctification that they hear. And they will despair about whether Christianity really works after all.
Or second, and maybe even worse, they will more or less make the sanctification changes that are called for, they will repent successfully of (some of) their sins, and the great danger then is spiritual pride, the oh-so-subtle vibe that people can give off that they make the grade.
Of course, any time you leave grace behind it results in either despair or pride, because it's only grace that can lift us in our despair, and humble us in our pride.
It's worth asking yourself the question - what was the implied spiritual dynamic of change in my last sermon / Bible study / conversation? Have I inadvertently been working with an approach which holds firmly to justification by grace through faith, but sanctification by willpower through works?
In which case, the question becomes, how do we preach and teach and pastor sanctification by grace through faith? That's the subject of the second part of this brief series.