We talk about the three “uses” of God’s Law. I like the Lutheran shorthand for these three uses: curb, mirror, and guide. As a curb, God’s Law restrains sin (1 Tim 1:8-10; Gal 5:19-21, etc.). As a mirror, it shows us our sin – and drives us to Christ (Rom 3:20, 7:7-8:4; Gal 3:10-14, 21-25, etc.). And as a guide, it shows us the works we are to walk in out of gratitude for God’s grace (Eph 2:8-10; Titus 2:11-14, etc.). Two things we need to keep in mind: the Holy Spirit is sovereign (John 3:8, 16:8-11, etc.), and the Law always convicts us of sin (Rom 4:15, 7:10, etc.). So we can’t presume that our intended “use” of the Law will stay within its bounds! We aren’t sovereign. The Holy Spirit is.
For example, a preacher may intend the “guide” use, e.g., here is a sermon on how you are to live in a Christian marriage. But the Law inherently accuses us that we fall short of its perfect standard. This convicting work of the Spirit through the Law is to be expected. And He may well decide to ramp that up in the conscience of the hearer. Take, “Husbands, love your wives as Christ loved the Church” (Eph. 5:25). This is an imperative. It is Law. As we hear this Scripture, the Spirit curbs our tendency to be self-centered jerks in our marriage. He clearly guides us in how we are to live as Christian husbands. And He always shows us how far short we fall of the perfect, self-sacrificing love of Christ.
And yet that is our very confidence as sinners – the perfect, self-sacrificing love of Christ. The Holy Spirit not only convicts us of sin, but His primary office is to point us to Christ (John 16:13-15). And so we need to be sure to ground the imperatives of the Law in the grace of the Gospel – even as Paul does in this very verse. Let the preacher understand! Law and Gospel must always be distinguished, yet never separated. The Law kills our flesh, and the Gospel raises us up as new creatures in Christ – who delight to walk in the good works God has prepared for us. The sovereign Spirit works through the Law to deepen our repentance. And He works through the Gospel to nourish our faith – that this Spirit-wrought, Gospel-fed faith would work through love (Gal 5:6).