In his letter to the church in Corinth, Paul declares, “Therefore, if anyone is in Christ, he is a new creation. The old has passed away; behold, the new has come” (2 Cor. 5:17 ESV). If this is true, that in Christ we are a “new creation,” why do I still struggle with sin? Shouldn’t I be free from the temptations that used to rule my life? Every believer, new or mature, young or old faces the challenge of persistent sin in his life. In this essay, I will discuss this issue as well as how our status as being justified in Christ relates to our sanctification in Christ.
To begin with, it’s important to understand what justification and sanctification are, as well as how they are different and how they are related. Calvin said, “The doctrine of Justification is … the principal ground on which religion must be supported, so it requires greater care and attention. For unless you understand first of all what your position is before God, and what the judgment which he passes upon you, you have no foundation on which your salvation can be laid, or on which piety towards God can be reared.” Justification, according to Calvin, is the foundation of our salvation and the spring of our devotion to God. Without a proper understanding of justification, therefore, we have no assurance of a right relationship with God and lack the means to live in a way that pleases Him.
When we speak of justification, we consider two actions—our sin credited to Christ and His righteousness credited to us. One of the verses that most clearly illustrates this great exchange is 2 Cor. 5:21, “For our sake he made him to be sin who knew no sin, so that in him we might become the righteousness of God” (ESV). Our sin can be credited to Christ only because of His one-time atoning sacrifice for sin at the cross, and his righteousness can be credited to us because He lived a life of perfect obedience to His Father. Our reception of Christ and all his benefits happen only through faith, and the Holy Spirit grants this faith to us. Faith by itself is nothing; it is only the means by which Christ is united to us, “For by grace you have been saved through faith. And this is not your own doing; it is the gift of God” (Eph. 2:8 ESV).
Another important aspect of justification is that it is a legal declaration of righteousness given to the sinner based on the mediatory work of Christ. It is not that the sinner has forthwith been transformed into a righteous person, but simply that the “demands of the law have been fully met” in Christ and therefore credited to the sinner as a result of his union with Christ through faith (Rom. 5:1, 9; Gal. 2:16). This language is not at all odd when we consider Paul’s discourse regarding Adam’s federal headship which “imputes guilt and condemnation as well as imparting inherent corruption [to mankind], while Christ’s federal headship imputes righteousness and imparts his inherent new life” (Romans 5).
One final point regarding justification is that it is not based on faith in Christ plus something else. This is in stark contrast to the Roman Catholic position, which holds that faith plus good works are the instrument of justification. Again Paul makes this point clear in his letter to the church in Rome, “But if it is by grace, it is no longer on the basis of works; otherwise grace would no longer be grace” (Romans 11:6 ESV).
As we consider the topic of sanctification in the life of the believer, it’s important to understand that though sanctification and justification are two separate realities, “justification is the judicial ground of a union with Christ that also yields renewal and sanctification.” In other words, a person will not grow in holiness if he is not first united to Christ through faith. “Faith is the essential motivation for genuine, God-pleasing obedience.” The author of Hebrews describes this connection, “And without faith it is impossible to please him” (11:6 ESV; cf. Rom. 1:5, 16:26).
In the Bible, sanctification speaks of God separating “people, places, and things away from their ordinary association for his own use.” It is the action of God claiming and setting people apart from the world for His own special purpose. Sanctification is not a matter of the Christian continuing the process that God began in justification, but “is the work of the Holy Trinity in which the reconciled sinner is renewed for the active life of holy fellowship with God.” In sanctification, the gospel work that God begins in justification continues to be unfurled in the life of the believer. Michael Horton says it well, “Where most people think that the goal of religion is to get people to become something that they are not, the Scriptures call believers to become more and more what they already are in Christ.” In sanctification, by God’s grace, we are in the process of becoming who we are.
Yet as followers of Christ we have the vital responsibility to “die daily to sin and rise anew in faith and repentance.” As redeemed sinners we are not simply called to ““let go and let God,” … and to abolish all consciousness of self.” Though God is our source of holiness, He works through means such as the hearing of the Word, private devotions, prayer, Christian fellowship, and the sacraments to conform us after the image of Christ. In his second epistle, Peter encourages his fellow brothers and sisters in Christ to “make every effort to supplement your faith with virtue, and virtue with knowledge, and knowledge with self-control, and self-control with steadfastness, and steadfastness with godliness, and godliness with brotherly affection, and brotherly affection with love. For if these qualities are yours and are increasing, they keep you from being ineffective or unfruitful in the knowledge of our Lord Jesus Christ” (2 Pet. 1:5-8 ESV). Far from being a willful detachment from reality, our growth in sanctification engages our will as we intentionally seek after God, yet all the while knowing that He is the vine, and outside of Him we can do nothing (John 15:4-5).
Still the question remains, why do we continue to struggle so desperately with sin? Horton describes this as a paradox—on one hand we are liberated from sin in Christ and are a new creation, yet on the other hand we live in this evil world and “continue to pretend that we are not those whom God has worded us to be in Christ.” We are simultaneously just as well as sinner. Paul describes this conflict as due to indwelling sin—rebellion that remains though we are justified in Christ, “For I know that nothing good dwells in me, that is, in my flesh. For I have the desire to do what is right, but not the ability to carry it out. For I do not do the good I want, but the evil I do not want is what I keep on doing. Now if I do what I do not want, it is no longer I who do it, but sin that dwells within me” (Romans 7:18-20 ESV). One commentator describes Paul’s conflict this way, “Paul’s experience convinced him that “the Law is good” (v. 16). But he also concluded, I know that nothing good lives in me. Then he hastened to explain that by the phrase “in me” he meant in my sinful nature (sarki, “flesh”; cf. vv. 5, 25). This is not literal physical or material flesh, but the principle of sin that expresses itself through one’s mind and body.
Michael Allen explains the conflict we experience as redeemed sinners using an adoption metaphor to describe our relationship to God in this fallen world. In justification, as in adoption, we receive an immediate legal declaration of adoption into the family. Yet the process of growing and conforming to our new identities is an ongoing process. Because our adoption (justification) is sure we are enabled to grow (be sanctified) in Christ. Our security in adoption provides the basis and motivation for our conformity to the family.
 John Calvin and Henry Beveridge, Institutes of the Christian Religion, vol. 2 (Edinburgh: The Calvin Translation Society, 1845), 302.
 Michael Horton, The Christian Faith: A Systematic Theology for Pilgrims on the Way (Grand Rapids, MI: Zondervan, 2011), 621.
 Ibid., 624.
 Ibid., 631, 632.
 Ibid., 631.
 Ibid., 632.
 Ibid., 626.
 Ibid., 649.
 Michael Allen, “Evangelical Holiness: Sanctification by (but not of) Faith Alone,” 1.
 Horton, The Christian Faith, 650.
 Ibid., 650-51.
 John Webster, Holiness, 78.
 Horton, The Christian Faith, 652.
 Ibid., 654.
 Ibid., 674.
 Ibid., 655.
 Ibid., 658.
 John A. Witmer, “Romans,” in The Bible Knowledge Commentary: An Exposition of the Scriptures, ed. J. F. Walvoord and R. B. Zuck, vol. 2 (Wheaton, IL: Victor Books, 1985), 468.
 Michael Allen, “Salvation and Eschatology,” Systematic Theology 604, Module 18 (Knox Theological Seminary: 2013).