(Taken from Brothers, We Are Not Professionals by John Piper, pages 25-27)
Romans 4.5 is perhaps the most important verse on justification by faith alone in all the New Testament. Three bright signals in this verse teach that justification is by faith alone and nothing but faith.
And to one who does not work but trusts him who justifies the ungodly, his faith is reckoned as righteousness (Romans 4.5)
First, he says, “To the one who does not work.” This does not mean there will be no “good works” that follow in sanctification. Paul takes that up in chapter 6 of Romans. We are dealing here with the moment of justification. This moment could happen for any of your people any Sunday morning in an instant because it is not a long process (like sanctification). Justification is a verdict delivered by God in a moment. And Paul says it happens to the person who “does not work”! That means in comes by faith alone.
The second signal that justification is by faith alone is the word “ungodly.” This is utterly shocking. It jars all of our judicial sentiments. It makes us cry out, “How can this be?” And the stupendous answer is that “Christ died for the ungodly” (Romans 5.6). God can justify the ungodly because His Son died for the ungodly. When faith is born in the soul, we are still ungodly. Faith will begin to overcome our ungodliness, but in the beginning of the Christian life, where justification happens, we are all ungodly.
Finally, the third signal that justification is by faith alone is the last phrase, “his faith is counted as righteousness.” Not his works, or his love, or even his fruit of faith, but his faith, his faith alone, is counted as righteousness.