Peace with God
"Therefore, since we have been justified by faith, we have peace with God through our Lord Jesus Christ."
Although Romans 3:21–4:25 covers in great detail the new status of righteousness that we enjoy in Christ by faith alone, the end of chapter 4 does not conclude the Apostle Paul's discussion of justification. As we will see in Romans 5:12–21, he still has much to say about how this status of righteousness is constituted. Given that the gospel message of what it means to be righteous in Christ is such good news, however, it is unsurprising that Paul gets caught up describing all the benefits we enjoy as a consequence of justification before he finishes his teaching on this doctrine. Romans 5:1–11 consists of a type of parenthesis wherein Paul pauses in the midst of his teaching on justification to answer this question: what does being declared righteous in Christ mean for us now? Verse 1 gives us the first part of that answer. Because we have been justified, we have peace with God.
We cannot understand the full ramifications of this peace unless we are fully convinced of what our relationship to our Creator was truly like before we knew Jesus. Scripture describes this relationship as an all-out war. Contrary to many popular ideas about God and humanity, the Lord's attitude toward fallen men and women who are outside of Christ is not one of kind benevolence or even neutral toleration. To be sure, our Maker is kind to some degree even to His enemies, but His disposition toward impenitent sinners is hostility and hatred. His bow is aimed at sinners, and He will release the arrows of the full fury of His wrath against people who remain opposed to Him (Ps. 7:12–13). Because no one seeks the Lord apart from grace (Rom. 3:9–18), this means that His ire is directed at every man, woman, and child who is not in Christ.
The Old Testament prophets understood this quite well, and they saw that God was at war with even the covenant community of Israel because of its sin. We read continual warnings about the consequences of this war in Scripture, namely the destruction of the exile, which foreshadows the eternal judgment of those who reject the Lord's rightful reign (Jer. 13:15–27; Ezek. 21; Dan. 12:1–2). But the prophets foresaw a great day of salvation when God would save His people and bring them shalom—peace—ruling them by His anointed king (Isa. 32). This shalom is not the mere cessation of hostilities but is much more. Shalom is a holistic concept, a condition in which people enjoy complete and permanent well-being. Romans 5:1 tells us that because we are justified, we enjoy this shalom.
Coram Deo
Perhaps the most important thing to understand about shalom is that it can never be lost. Jesus has not brokered a fragile cease-fire with God, such that full-scale conflagration can erupt at the slightest provocation. Instead, He has brought us a peace that can never be lost. If we are truly in Christ, we will never become His enemies again. Dr. R.C. Sproul writes in his commentary on Romans, "Christ is our peace, so for us there is no more war with God."