The doctrine of justification is at the heart of the gospel, for justification explains how we are found acceptable to God. To understand this doctrine, then, is to understand the gospel itself.
Like the other doctrines explained in the New Testament, justification can be understood only against its Old Testament background. First, we must understand what happens in justification. In justification, God solves the legal or judicial problem that we have on account of our being lawbreakers who have violated His commandments, and He does so by means of a legal declaration of our status, not by inward transformation. In Deuteronomy 25:1, judges are commanded to be in the business of “acquitting the innocent.” Clearly, when a judge acquits an innocent person, he is not changing that person but merely making a declaration about that person’s status before the law. Having considered the evidence, the judge declares legally that the defendant is not a lawbreaker based on the evidence. Notably, the word “acquitting” translates the Greek verb dikaio , which is the same verb used in Romans 4:5 when Paul says that God justifies the ungodly. In justification, God does not change a person, although all who are justified have been given a new heart to believe in Christ. In a manner similar to that of an old covenant judge, God, the great Judge, considers the facts of the case and pronounces sinners righteous in His sight.
But what are the facts upon which the Lord justifies us? As we have seen, the righteousness of Christ is the basis for our justification. We must have faith, but faith itself is not the righteousness that justifies us. If it were, then our justification would be based on something we do, since we believe in Christ, and Paul is adamant that justification is not based on any human action or effort (Rom. 4:1–2). Saving faith is pleasing to God, but as even our faith is imperfect, it cannot serve as the meritorious basis for our justification. This is alluded to in today’s passage, where it would be more accurate to translate “his faith is counted as righteousness” in Romans 4:5 as “his faith is counted unto/for the end of righteousness.” Our faith is the instrument of justification because through it God counts or imputes the perfect righteousness of Christ to our account. Our faith is unto righteousness—it is the means through which we receive the obedience of Christ, which is the righteousness that justifies us.