Mike Horton, in Christ the Lord:
As Christ is the answer to our guilt and condemnation (through justification), so he is the answer to our bondage and corruption (sanctification). He takes away not only the verdict, but also the slavery. To justify us in the heavenly court without giving us the gifts that, by virtue of that heavenly verdict, belong to us would be cruel and unjust on God’s part. No, he does not simply put money into our bank account and then leave us stranded along the side of the road, beaten and bruised.
Holiness is not an option for the Christian. But hold on — I can hear the hearts racing: “Holiness, the impossible dream?” To be sure, “but with God all things are possible” (Matthew 19:26). Holiness is not an option; it is a requirement.
But this is not a threat. It’s a promise. What God began he will finish (Phil 1:6). In Christ we are already holy, righteous, sanctified, reconciled (1 Cor 1:30). Now we are called to live what we are, not to become what we are not yet.