What is the unforgivable sin?

Short answer

The unforgivable sin is blasphemy against the Holy Spirit: knowingly and stubbornly calling the work of God the work of Satan, and so rejecting the very One who leads to repentance. Anyone who is troubled by this and wants forgiveness shows that he has not committed it, because Christ promises to forgive those who confess.

Few phrases in the Bible frighten people as much as “the sin that will not be forgiven”. Some fear they may have committed it by a wrong thought or an angry word. To understand what Jesus meant, we need to see what was happening when He said it.

What Jesus said and to whom

Jesus had just driven a demon out of a man. The Pharisees had an answer for this: He casts out demons by Beelzebul, the prince of demons. In reply Jesus gave a solemn warning.

Wherefore I say unto you, All manner of sin and blasphemy shall be forgiven unto men: but the blasphemy against the Holy Ghost shall not be forgiven unto men. And whosoever speaketh a word against the Son of man, it shall be forgiven him: but whosoever speaketh against the Holy Ghost, it shall not be forgiven him, neither in this world, neither in the world to come.
Matt 12:31–32 · King James Version (1769)

Mark records the same words and adds why Jesus said them.

Verily I say unto you, All sins shall be forgiven unto the sons of men, and blasphemies wherewith soever they shall blaspheme: But he that shall blaspheme against the Holy Ghost hath never forgiveness, but is in danger of eternal damnation:
Mark 3:28–29 · King James Version (1769)

Albert Barnes explains that the sin lay in saying that Jesus worked His miracles by the devil and not by the Spirit of God, and he points to Mark’s closing words (Mark 3:30), which give the reason for the warning. William MacDonald describes it in the same way: in effect the scribes called the Holy Spirit the prince of demons. John MacArthur stresses that this was a deliberate rejection of what the Pharisees knew came from God. They could not deny what the Spirit did through Jesus, so they credited it to Satan.

Why this sin cannot be forgiven

At first it seems odd that Jesus says every other sin and blasphemy can be forgiven, even a word against the Son of Man. Jamieson, Fausset and Brown observe that this wide promise must not be limited by what follows. Their conclusion is that the sin is not unpardonable because of something in its own nature, since that would contradict the promise that all sins can be forgiven. The difference lies in the position of the person.

MacArthur explains that someone who has never seen the power of Christ can reject Him in ignorance and still be forgiven if he repents. He recalls Saul of Tarsus, who persecuted the church in ignorance and received mercy (1 Timothy 1:13). But those who know His words are true and reject Him anyway sin against the Spirit, because the Spirit is the One who bears witness to Christ. The New Geneva Study Bible puts it simply: this blasphemy is a clear, firm and conscious rejection of the very Power that leads people to repentance. There is no forgiveness because the person refuses the only way to receive it.

Can I have committed it?

Christians have understood this a little differently. MacDonald thinks there is reason to doubt that the sin can be committed today in the same way, because Jesus is not on earth in the body, working miracles. He also notes that it is not the same as rejecting the gospel: a person can scorn the gospel for years and still be saved. MacArthur, in his notes on Mark, speaks more widely: whoever deliberately and irreverently slanders the work of the Spirit and so rejects Christ loses any claim to forgiveness.

Whichever view one takes, the pastoral point is the same. Matthew Henry writes that humble and conscientious believers are often tempted to think they have committed the unpardonable sin, while those who have come closest to it seldom fear it. Those who truly repent and believe the gospel have not committed it, because repentance and faith are gifts of God, and He does not give them to someone He has decided never to pardon. Those who fear it are thereby showing a good sign. The New Geneva Study Bible agrees: anyone who has come to believe the truth can no longer commit this sin.

The promise stays open

The same Bible that warns us also makes a clear promise.

If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.

1 John 1:9 · King James Version (1769)

MacArthur sees in constant confession of sin a sign of true salvation: genuine Christians admit their sins and want to be free of them. MacDonald adds that real confession means calling sin by its name, taking God’s side against it and leaving it behind.

If you are troubled by your sin and want to be forgiven, that is not the picture of the Pharisees, who hardened themselves against the light. Bring your sin to God and ask Him to forgive. Christ stands ready to do so (Matthew 11:28).