1 John 3:5
"You know that He appeared in order to take away sins; and in Him there is no sin."
1 John 3:8
"The Son of God appeared for this purpose, to destroy the works of the devil."
Same event.
Two complementary purposes.
The removal of sin and the undoing of the devil’s works are not two separate missions; they are the same mission seen from two angles. The moral seriousness of the Christian life is grounded in this appearing of the sinless Son who both removes sin and destroys the devil’s works. Therefore the children of God are being made new. Not grounded in human resolve or religious effort. Therefore the practical force is clear; if this is why He appeared, then the believer who continues in the practice of sin is living as though the purpose of the incarnation has failed. And it can be frustrating for one who is anointed in the Spirit to have this truth and be in communion with some who do not.
The one who sees the weight of these verses, and who lives under their force, to walk in regular communion with people who treat the same truths as optional, theoretical, or secondary is extremely disheartening. John himself lived in that tension. The letter is written precisely because some were claiming fellowship with God while denying the moral seriousness of the appearing. Some said they had no sin. Some continued in practice of sin while claiming to know Him. Some separated themselves. John does not soft-pedal the dissonance. He names it, distinguishes the children of God from the children of the devil, and still calls the faithful to remain in the truth and in love.
Now, why do you suppose John wrote to "the faithful" to remain in the truth and in love? Is it possible that these "faithful" are in danger from being led astray? If so, how. Aren't these them who have the Spirit securing their bond with the Lord?
I believe it's obvious in the testimony of every apostle, who have written their witness for us to read even now, that there is a danger that even the most faithful followers face. It is clear by these writings that every believer still lives in a contested field where deception is active and the pull toward compromise is constant. No one is invulnerable. No one is immune to deception. Even though they study in the Spirit, and remain in their faith, they are susceptible to deception.
The Apostles write as men who themselves know both the reality of the Spirit’s sealing and the reality of the contested field. They never present the believer as invulnerable. They present the believer as secured and still required to watch, remain, test, and hold fast.
"The spirit indeed is willing, but the flesh is weak." (Matthew 26:41)
"The Spirit clearly says that in later times some will abandon the faith and follow deceiving spirits and things taught by demons." (1 Timothy 4:1)
Jesus does not say the spirit is unwilling. And He does not say the flesh is sovereign over the human will. He simply states the condition under which even the most earnest disciples live; a real willingness that can still be overpowered by weakness if they do not watch and pray.
Jesus' warning was not theoretical. Within hours they all fled from him.
These warnings are not addressed only to the false professors from the start.
The same Spirit who seals, anoints, and teaches is the One who warns that some among all will abandon the faith. This should dispel every notion that a follower cannot end up in a fallen state or experience more than their faith can sustain. Jesus, Paul, Peter, John, and Jude all speak as though the danger is genuine and the outcome is not automatic.
Jesus and the apostles speak of a living relationship that must be lived in. They treat perseverance as something the believer must actually do, empowered by the Spirit, rather than something that happens to the believer irrespective of response. At the same time there is a tension between assurance and assumption.
The natural conclusion is there is a confidence that the One who began the work is faithful, that His sheep are held in His hand, and that those who go out ultimately show they were not of the fold. The tension is left unresolved in the text. And it is not a problem to be solved. It is the condition under which the church has been established, left to cope with and in which they should live between the first appearing and the second.
There is real confidence, and real tension. No one is absolved from this fact. Scriptures refuse to let that confidence become presumption, and they refuse to let the warnings become grounds for despair. We must live inside the interval. The Son has already appeared to take away sins and to destroy the works of the devil. The children of God are already being made new. And the contested field remains contested until He appears again. It is the shape of discipleship until the day we see Him as He is.
We pray for it.
We watch for it.
We walk in it.
We run from everything that suggests otherwise.
That is how the tension is lived out rather than resolved.
It's a little like TRT. Some men can experience the benefits of testosterone replacement if they have reduced testosterone systems. Yet, at the same time these artificial means can condition the body to not naturally produce testosterone, so that if the supplemental testosterone is interrupted the body is no longer prepared to produce even reduced levels anymore.
Supplemental testosterone can restore energy, strength, and clarity when natural production has declined. But the body is adaptive. The cure can become a problem.
Spiritually, something parallel can happen. Certain forms of teaching, church structures and doctrines, assurance language, or even disciplined religious habits can supply real benefits. They can steady a man, clarify truth, and protect him for a season. But if those externals begin to function as a substitute for direct, ongoing dependence on the living Christ; if they quietly condition the heart to rely on the religious prop rather than on the One who appeared to take away sins and destroy the works of the devil, then the "natural" capacity to abide, to watch, to test, and to remain can atrophy. In other words, the spirit is willing but the flesh is weak.
The spirit can remain willing while the flesh, conditioned by reliance on secondary things, grows weaker in the very capacities that matter most. What was meant to support living dependence can, over time, train the heart to lean on the support instead of on the One the support was meant to point toward. This is why the apostles are so jealous for direct attachment to Christ Himself. Teaching scriptures, building structure, sound doctrines, assurance rooted in the finished work, and disciplined habits are all good gifts. They are not the enemy. The danger arises only when any of them begins to function as a functional substitute for ongoing, personal dependence on the Son who appeared to take away sins and to destroy the works of the devil.
When that substitution occurs, the atrophy is real. The willingness is still real, but the trained capacity to live from the Source has diminished. And one profound symptom is a sort of spiritual brain fog.
The willingness may still be present. The person may still affirm the right doctrines and feel a residual desire for God. But clarity dulls. Discernment slows. The edge of spiritual perception blunts. The believer loses spiritual nerve. What should be present as steady spiritual virility becomes passivity, hesitation, and a dulled edge. The believer is neutered.
The only recovery is the return to the Source Himself. Everything else must be put back in its secondary place, or the atrophy will continue.