The tragic, inescapable reality of the believer’s life is that he or she will never totally and finally conquer sin. The Lord has transformed us, replaced our hearts, and reoriented our lives, but we still can’t completely escape the grip of sin.

The apostle John recognizes, of course, that believers do fail and fall into sin. As a matter of fact, he began the epistle with a series of statements underscoring the truth that no one can claim any degree of perfection in this life: “If we say that we have no sin, we are deceiving ourselves and the truth is not in us” (1 John 1:8). And, “If we say that we have not sinned, we make Him a liar and His word is not in us” (1 John 1:10). When we sin, however, Christ is our advocate with the Father (1 John 2:1) as well as the all-sufficient sacrifice who has paid the price of our sin (1 John 2:2).

Therefore, we can know true assurance, despite the sinful and fleshly tendencies we all struggle with. Read Paul’s testimony in Romans 7 about his own frustrating battle to overcome the sin that remains in each one of us as long as we inhabit fallen flesh. We all sin all the time, and we wage the very same struggle Paul describes in Romans 7:14-24. But notice that Paul ends that discussion with a celebration of his own assurance: “Thanks be to God through Jesus Christ our Lord!” (Romans 7:25). From there, he devotes the entirety of Romans 8 to a discourse about the believer's security in the Spirit.

How can believers know that kind of assurance, even while being aware of their own sinfulness?

First, it’s vital to understand that Scripture expressly refutes all forms of perfectionism. Even when the apostle John writes, “No one who is born of God practices sin, because His seed abides in him; and he cannot sin, because he is born of God” (1 John 3:9), he is clearly not making perfection a test of salvation, because as we have seen, he recognizes and even emphasizes the inevitability of sin in every believer’s life.

The point of 1 John 3:9 has to do with our attitude toward sin and righteousness, our response when we do sin, and the overall direction of our walk. In other words, as I have often said, we don’t test the genuineness of our repentance by the perfection of our walk, but by the direction of it. In the words of Puritan John Owen, "Your state is not at all to be measured by the opposition that sin makes to you, but by the opposition you make to it."¹John Owen, The Works of John Owen 16 vols. (London: Banner of Truth, 1996 reprint), 6: 605.

What is the true moral object of your affections? Is it sin or righteousness? If your chief love is sin, then according to the principles outlined in 1 John, you are “of the devil” (1 John 3:8, 10). If you love righteousness and practice righteousness, you are born of God (1 John 2:29). This is not measured by the frequency, duration, or magnitude of one’s sins, but by the inclination of the heart.

And the true mark of a redeemed heart is a spirit of repentance, mourning over our sin when we do fall, and a deep and abiding dependence on God’s grace as we wage the warfare against sin. To quote John Owen once more: "A man, then, may have a deep sense of sin all his days, walk under the sense of it continually, abhor himself for his ingratitude, unbelief, and rebellion against God, without any impeachment of his assurance."²Ibid., 6: 549.

That may sound preposterous, but an understanding of the depth of our own sin is the very thing that keeps Christians from falling into utter despair. We know we are guilty, fallen, and frail. To use the exact idea conveyed in the Greek text of 1 John 1:9, we agree with God about our sin.

When we discover sin in our lives, we are not shocked or astonished, but we nonetheless hate the fact that it is there. We trust Christ, our Advocate, for forgiveness and cleansing. And far from becoming tolerant or comfortable with sin in our lives, we become more and more determined to mortify it. As John says, “I am writing these things to you so that you may not sin” (1 John 2:1, emphasis added).

In other words, a spirit of perpetual repentance ought to permeate and characterize the life of every true believer. The repentance that takes place at conversion begins a progressive, lifelong process of confession and forgiveness (1 John 1:9). That spirit of continual repentance in no way undermines the assurance of a true child of God. On the contrary, it is the very thing that feeds our assurance and keeps it alive.