A popular preacher and author wrote this in one of his books:

On the last day, God will not acquit us because our good works were good enough, but he will look for evidence that our good confession was not phony. It’s in this sense that we must be holy.

That perspective is a backwards motivation for holiness. It’s soul crushing for Christians of weak-conscience. 

Unfortunately, New Calvinists have created a culture of fear when it comes to personal holiness. I, for one have been damaged by this kind of pietistic, revivalistic teaching around obedience. And it seems like most of American Evangelicalism can’t talk about holiness without questioning one’s salvation or motivating one with guilt. There is no rest for the Christian believing in this motivation. It begs the question, “How many good works must I perform for God to consider my faith authentic?” How holy do I have to be to know that I’m saved?

So we ask again “Why be holy if Christ alone saves?” Well, the answer is in the question. Christ alone saves! Christ completed perfect obedience to the law of God that we couldn’t achieve, died the death that we deserved, and resurrected so that we too will resurrect from the dead. If you are in Christ, you have been justified in God’s sight. Our debt of sin was transferred to Christ’s account, and He paid for it (Colossians 2:14). Christ’s righteousness was transferred to our account, and because of Him we inherit eternal life (Romans 5:21). For all who are in Christ, we are seen by God as if we have never sinned but also as if we had done everything right. As J.V. Fesko once said, “justification is the final verdict handed down in the present”. Perhaps we can amend the statement above to: On the last day, God will see what Christ accomplished on our behalf and we will enter into His warm embrace forever. It is in this sense that we must be holy. Assurance is central to the Reformed motivation for holiness. There are no conditions we must meet in order for us to have assurance. John Calvin writes concerning faith in the finished work of Christ:

This is the security which quiets and calms the conscience in the view of the judgement of God… (Institutes, 3.2.16)

For Calvin, and the Continental Reformed, assurance is found in the objective work of Christ, not in the subjectivity of personal holiness. Michael Horton defends this view of assurance as he writes,  

If assurance is not the essence of saving faith, and it can be lost because of sin, sensitive persons will inevitably scrape their consciences raw until they find clues and, as Calvin warned, there will be no satisfactions with evidences [our good works]; there will never be enough to secure the soul’s confidence (Christ The Lord, 134).

If you look to your own personal holiness as the ground of your assurance before God, you will never find rest. Trust me, I’ve tried. In fact, if fear is your motivation to obey, you will never be able to love God and your neighbor well.

The essential component in true faith is the trust that what is true of the gospel is not only true in general but true for me personally (Heidelberg Catechism 21). We confess with the Heidelberg Catechism that our only comfort in life and in death is that

I with body and soul, both in life and death, am not my own, but belong unto my faithful Savior Jesus Christ; who, with His precious blood, hath fully satisfied for all my sins, delivered me from all the power of the devil; and so preserves me that without the will of my heavenly Father, not a hair can fall from my head; yea, that all things must be subservient to my salvation, and therefore, by His Holy Spirit, He also assures me of eternal life, and makes me sincerely willing and ready, henceforth, to live unto Him.

The Heidelberg Catechism even answers this objection directly:

64. But doth this doctrine [justification by faith alone in Christ alone] make men careless and profane?

A. By no means: for it is impossible that those, who are implanted into Christ by a true faith, should not bring forth fruits of thankfulness.

Over the entire history of Christianity, those who have preached the unconditional grace of God have been accused of antinomianism (anti – against, nomos – law). As the etymology implies, antinomians see no place for the law of God in the Christian life. However, the orthodox have always been quick to not walk back what they said of the grace of God, but to clarify the use of the law in the Christian life. The end of the first question in the Heidelberg Catechism says that those who have received the glorious grace of God in Christ are “sincerely willing and ready, henceforth, to live unto Him.”

The Christian life ought to be lived as an overflow of joy and gratitude for what has already been done for us by our Lord Jesus Christ. We don’t strive for holiness to pay God back for sending His only Son to die for us, for Christ is of infinite worth that we “unworthy servants” could never repay (Luke 17:7-10). Instead, we should strive for holiness because hearts that are filled with God’s love have no choice but to overflow in love for Him and others.

Our Lord said to disciples, “If you love me, you will keep my commandments” (John 14:15). For our American Evangelical minds, we tend to interpret this as if Christ is holding a gun to our heads, accusingly questioning us on whether or not we love Him. In fact, we tend to read the Gospels as if Christ was always preaching against “easy-believism” (the ideology that teaches merely assenting to the facts of the Gospel makes one a Christian). In reality, however, He saved His harshest words for those who kept the people of God under the bondage of the law (Matthew 23:13-36). Christ stated this in His Upper Room Discourse (John 13-17) hours before His death, intending the discourse to encourage His disciples, not paralyze them with fear. If we take a closer look at the verse, the motivation for obedience is love for Christ. “If you love me, you will keep my commandments.” Obeying God out of love, rather than out of fear of receiving wrath, was a revolutionary idea in Jesus’ day. We must also note that this is a promise (“you will keep my commandments). The promise of the New Covenant is that God will put His Spirit within us and cause us to walk in His statutes and obey His rules (Ezekiel 36:27). For those who love Christ, we will obey Him for we can only do what’s proper to our new nature. Christ not only saves us from the guilt of sin, but from the power of sin as well. By virtue of our union with Christ (John 15:1-5), we have died to sin and raised with Him to walk in the newness of life (Romans 6:1-4). The moment we trust in Christ alone for our salvation, we are given the identity of “slaves of righteousness” (Romans 6:18). This is not an identity that we have to manufacture for ourselves but one that is freely given to us by the grace of God in Christ, which renders any notion of a “carnal Christian” (the idea that a Christian can be justified, and then not be sanctified unless he or she wills to do so) untenable.

1 John 4:19 states, “We love because he first loved us.” We love God and our neighbors solely because of God’s love for us. In love, the Father predestined you to be saved, not because He thought you were better than your pagan classmate or saw that you would be a “varsity Christian”, but solely out the generous pleasure of His will (Ephesians 1:5, Romans 9:16). The Father demonstrated that love in history by sending His only Son, Jesus Christ, to die and bear the wrath of God for us (Romans 5:8, 8:32). And then Holy Spirit came and changed our God-hating, sin-loving, Gospel-resisting hearts to hearts that embraced the Gospel, acquired a distaste for sin, and loves our gracious God (John 3:3-8, 2 Corinthians 4:4-6, 1 John 5:1). And because of God’s love, we have received “adoption as sons” (Galatians 4:5). We are no longer slaves to the fear of condemnation, but children of God, and if children of God, then heirs of eternal life through God (Galatians 4:7, Romans 8:14-17). Obedience driven from slavish fear does not please God. But obedience driven from that fact that we have peace with God, pleases our heavenly Father and honors the redemptive work of Christ.

As children of God and heirs of eternal life, we are given rules to how we ought to conduct ourselves in His Kingdom (i.e. God’s law). There are three uses to the law. In the first use, God acts as a judge “who will by no means clear the guilty” (Numbers 14:18). The purpose of the law is to condemn us and show us our need for Christ. However, Christ came and took our guilt upon Himself and satisfied God’s just wrath for our sins (Romans 3:23-26). In the second use, God acts as a governor who orders civil society (Romans 13:1-5). In the third use of the law, God acts as a loving Father who instructs us children. He does discipline those He loves (Hebrews 12:5-6), but He is not an abusive Father. He does not give His children black eyes. He still continues to accept us, even when we sin, solely because of His Son, Jesus Christ. As Matt Chandler likes to say, “God is not in love with a future version of you. He loves you right now.” And because He loves us so, He will not leave us as we are but will continually sanctify us so that He is more and more our delight.

It is in this sense that we must be holy.