For the Apostle Paul, the doctrine of justification was the heart of the gospel (Rom. 1 :17; 3:21-5:21; Gal. 2:15-5:1). Martin Luther declared that justification was the doctrine by which "the church either stands or falls." R.C. Sproul's mentor John Gerstner goes further in reminding us that it's not only the church that stands or falls by this doctrine, "but the individual also."
As justification is so important, it's necessary that we have a clear understanding of what this doctrine teaches. While reading Galatians in the The Reformation Study Bible recently, I appreciated the clear and succinct explanation offered in its theological article on justification.
Justification is God's act of pardoning sinners and accepting them as righteous for Christ's sake. In it, God puts permanently right their previously estranged relationship with Himself. This justifying sentence is God's bestowal of a status of acceptance for Jesus' sake (2 Cor. 5:21).
Justification is God's act of pardoning sinners and accepting them as righteous...
God's justifying judgment seems strange, for pronouncing sinners righteous may appear to be precisely the kind of unjust action by a judge that God's own law forbids (Deut. 25:1; Prov. 17:15). Yet it is a just judgment, for its basis is the righteousness of Jesus Christ. As "the last Adam" (1 Cor. 15:45), our representative head acting on our behalf, Christ obeyed the law that bound us and endured the punishment for lawlessness that we deserved, and so "merited" our justification. Our justification is on a just basis (Rom. 3:25, 26; 1 John 1:9), with Christ's righteousness reckoned to our account (Rom. 5:18, 19).
God's justifying decision is in effect the judgment of the Last Day regarding where we will spend eternity, brought forward into the present and pronounced here and now. It is a judgment on our eternal destiny; God will never go back on it, however much Satan may appeal against the verdict (Zech. 3:1; Rom. 8:33, 34; Rev. 12:10). To be justified is to be eternally secure (Rom. 5:1-5; 8:30).
To be justified is to be eternally secure...
The necessary means of justification is personal faith in Jesus Christ as crucified Savior and risen Lord (Rom. 4:23-25; 10:8-13). Faith is necessary because the meritorious ground of our justification is entirely in Christ. As we give ourselves in faith to Jesus, Jesus gives us His gift of righteousness, so that in the very act of "closing with Christ," as older Reformed teachers put It, we receive the divine pardon and acceptance we can find nowhere else (Gal. 2:15, 16; 3:24).
Find other helpful answers in the thousands of in-depth study notes and 96 theological articles included in The Reformation Study Bible.