What is the unforgivable sin?

What the Bible says

The saying comes right after Jesus drove out a demon. Scribes who had come down from Jerusalem said, "He is possessed by Beelzebul," and, "By the prince of the demons He drives out demons" (Mark 3:22). Jesus answered that a kingdom divided against itself cannot stand (Matt 12:25-26), and that he drives out demons "by the Spirit of God" (Matt 12:28). Then he said this.

Truly I tell you, the sons of men will be forgiven all sins and blasphemies, as many as they utter. But whoever blasphemes against the Holy Spirit will never be forgiven; he is guilty of eternal sin.”

Mark 3:28-29

Matthew's form adds a contrast.

Whoever speaks a word against the Son of Man will be forgiven, but whoever speaks against the Holy Spirit will not be forgiven, either in this age or in the one to come.

Matt 12:32

Notice how it begins: "all sins and blasphemies" are forgiven. The width of forgiveness is declared first, and then one exception is named. Even a word against the Son of Man, Jesus himself, can be forgiven. So what is the exception? Mark adds the reason: "Jesus made this statement because they were saying, 'He has an unclean spirit'" (Mark 3:30). The context is clear. God's work was done by the Spirit before their eyes, and they called it Satan's. That is not doubting or asking questions. It is turning from what looks like the road home and calling it evil.

Scripture also shows people forgiven who seemed beyond it. Paul says, "I was formerly a blasphemer, a persecutor, and a violent man; yet because I had acted in ignorance and unbelief, I was shown mercy" (1 Tim 1:13). And Jesus says, "the one who comes to Me I will never drive away" (John 6:37).

The church's witness

The church has read this saying in three main ways, each holding on to part of the text.

Final impenitence. Augustine called this perhaps the hardest question in Scripture. His conclusion: the first gift of believers is the forgiveness of sins in the Spirit, and against this gift the unrepentant heart speaks, so "impenitence itself therefore is the blasphemy against the Spirit which shall not be forgiven" Augustine. But he adds at once that while anyone lives, we cannot judge his impenitence, "for we must despair of none so long as the patience of God leads to repentance" Augustine. Forgiveness is blocked not because God refuses but because a person stays to the end without asking for it.

Knowingly opposing God's work. Jerome speaks of one who, "plainly perceiving the works of God, and being unable to deny the power of God, speaks falsely against them prompted by jealousy" Jerome. A word against the Son of Man can come from stumbling at his humble flesh, but calling the Spirit's work Satan's is a hardness that sees and still refuses. Some think this sin belonged to those who saw Jesus' ministry directly; others think a similar hardness remains possible. Thomas Aquinas drew these readings together under sins of deliberate malice, such as despair and obstinacy; the Catholic Catechism today speaks of deliberately refusing God's mercy.

Turning against grace once received. In his commentary on the Sermon on the Mount, Augustine asks cautiously whether it might be to attack brotherly love out of malice and jealousy after receiving the Spirit's grace Augustine. Later, in his Retractations, he called this uncertain and limited it to one who dies in that hardness.

Matthew Henry reads the saying as a pastor. "Humble and conscientious believers, at times are tempted to think they have committed the unpardonable sin, while those who have come the nearest to it, seldom have any fear about it" Matthew Henry. And: "The trembling, contrite sinner, has the witness in himself that this is not his case" Matthew Henry.

In the original languages

"Blasphemy" is blasphemia (βλασφημία), injurious speech against God or people. Here it names the direction of the heart more than a slip of the tongue, as Jesus goes on to say: "For out of the overflow of the heart the mouth speaks" (Matt 12:34).

"Forgiven" is aphiemi (ἀφίημι), "to release," as one releases a debt. With the negative, nothing is released. Many read the weight of the saying not as God being unable to release, but as release not happening where the heart refuses it.

Common objections

"If some sin cannot be forgiven, doesn't that put a limit on grace?" This is an honest question: if Christ's blood covers every sin, how can any sin remain? The church's answer is that the problem is not a shortage in Christ's blood but a refusal of the way forgiveness is received. Matthew Henry, writing on Hebrews 6, says this is "not because the blood of Christ is not sufficient to obtain pardon for this sin; but this sin, in its very nature, is opposite to repentance and every thing that leads to it" Matthew Henry. An open door does little for someone who has locked himself in. This interprets what Jesus did not explain; the text says only "eternal sin."

"I have had blasphemous thoughts about God. Maybe I committed that sin." This is one of the commonest fears among sincere Christians. First, plainly: an unwanted blasphemous thought, words of anger or pain flung at God, and doubt are not this sin. The psalmists protested to God in rough language. Those who commit this sin are usually not afraid of it, and the person who trembles and asks forgiveness is still facing God. The LORD is "near to the brokenhearted" (Ps 34:18), and "a broken and a contrite heart, O God, You will not despise" (Ps 51:17). "If we confess our sins, He is faithful and just to forgive us our sins" (1 John 1:9). Matthew Henry says that those who truly repent and believe can be sure they have not committed it, because repentance and faith are God's gifts Matthew Henry. This is not a reading of the heart but a well-grounded comfort from Scripture. If the same thought keeps returning until daily life is hard, speak with a pastor or counselor you trust. Such fears often come from a weary mind, not weak faith.

"Don't Hebrews 6 and 1 John 5 describe a sin with no way back?" They do. Hebrews says of those who have shared in the Holy Spirit "and then have fallen away" that it is "impossible… to be restored to repentance" (Heb 6:4-6). John says, "There is a sin that leads to death; I am not saying he should ask regarding that sin" (1 John 5:16). Arminians take them as warning that a true believer can finally renounce Christ; the Reformed take the warnings as a means of perseverance, and those who fall away as never truly belonging. John does not say what "death" is, and he does not forbid prayer. In most readings both describe knowing, open renunciation of Christ, not weakness or a temporary fall. Matthew Henry warns that we must not "wound and terrify the weak, or discourage the fallen and penitent" Matthew Henry.

Going further

This saying is a warning, not a source of dread: do not let your heart harden toward God's work or close your ears to the Spirit. The Spirit is the one who "will convict the world in regard to sin and righteousness and judgment" (John 16:8). If you feel the pain of sin, you can read it as the Spirit still at work, and that pain should lead not to despair but to Christ.

Ask yourself: am I putting off asking forgiveness? Do I believe that Christ drives away no one who comes to him? If someone near me fears this sin, what could I say to him?

To read further, see What is repentance?, Who is the Holy Spirit? and Can salvation be lost?.