Here is an excerpt from The Hole in Our Holiness:
Let me be clear about something from the very beginning: stressing the necessity of personal holiness should no undermine in any way our confidence in justification by faith alone. The best theologians and the best theological statements have always emphasized the scandalous nature of gospel grace and the indispensable need for personal holiness. Faith and good works are both necessary. But one the root and the other the fruit.
The impact of the gospel results in the changed life of the individual. The seed of the gospel bears fruit so it is right to expect and look for growth in holiness from people to claim to be followers of Christ.
DeYoung goes on to say:
Any gospel which purports to save people without transforming them is inviting easy believism. If you think being a Christian is nothing more than saying a prayer or joining a church, then you’ve confused real grace with cheap grace. Those who are justified will be sanctified.