What is the unforgivable sin?

The sin of blaspheming the Holy Spirit is a sin that could only be committed in the time of Jesus’ first coming. It is not a sin that a Christian can commit today. This sin has occurred only once in history, as recorded in Matthew 12:

Matt. 12:22   Then a demon-possessed man who was blind and mute was brought to  Jesus, and He healed him, so that the mute man spoke and saw. 
Matt. 12:23   All the crowds were amazed, and were saying, “This man cannot be the  Son of David, can he?” 
Matt. 12:24   But when the Pharisees heard this, they said, “This man  casts out demons only by  Beelzebul the ruler of the demons.” 
Matt. 12:25   And  knowing their thoughts Jesus said to them, “Any kingdom divided against itself is laid waste; and  any city or house divided against itself will not stand.
Matt. 12:26  “If Satan casts out Satan, he  is divided against himself; how then will his kingdom stand?
Matt. 12:27  “If I by Beelzebul cast out demons, by whom do your sons cast them out? For this reason they will be your judges.
Matt. 12:28  “But if I cast out demons by the Spirit of God, then the kingdom of God has come upon you.
Matt. 12:29  “Or how can anyone enter the strong man’s house and carry off his property, unless he first binds the strong man? And then he will plunder his house.
Matt. 12:30  “He who is not with Me is against Me; and he who does not gather with Me scatters.
Matt. 12:31  “Therefore I say to you, any sin and blasphemy shall be forgiven people, but blasphemy against the Spirit shall not be forgiven.
Matt. 12:32  “Whoever speaks a word against the Son of Man, it shall be forgiven him; but whoever speaks against the Holy Spirit, it shall not be forgiven him, either in this age or in the age to come. 

In this scene, Jesus performed an important miracle. He healed a mute man possessed by a demon. In Jewish tradition and teaching, the Messiah was said to be recognizable on the basis of three unique miracles only He could perform. The three "Messianic miracles" were healing a leper, healing a man born blind and casting out a demon from a mute man. In Matthew 12 we see Jesus performing the third of these three Messianic miracles.

Why is casting out a demon from a mute man considered proof of the Messiah? The answer comes from an understanding of how Jewish rabbis performed exorcisms in Jesus' day.

Casting out of demons (exorcisms) were commonly performed in Israel by rabbis and priests. (We can see evidence that exorcism was practiced in the first century in the story found in Acts 19 of the seven sons of the Jewish priest, Sceva.)

The Jewish manner of casting out demons could only be accomplished through a very specific ritual handed down by tradition (and presumably originating in divine revelation). Specifically, to cast out a demon, the priest had to call the demon out by name. So, in order to cast out a demon, the priest had to learn the demon's name. 

To learn the name of the demon, the priest would inquire of the demon, and the demon would answer by speaking using the voice of the human body it inhabited. Once a priest knew the demon’s name, he then could perform the exorcism by casting out the demon by name. Jesus followed this same procedure at times, as we see in another account in Luke:

Luke 8:26  Then they sailed to the country of the Gerasenes, which is opposite Galilee. 
Luke 8:27  And when He came out onto the land, He was met by a man from the city who was possessed with demons; and who had not put on any clothing for a long time, and was not living in a house, but in the tombs. 
Luke 8:28  Seeing Jesus, he cried out and fell before Him, and said in a loud voice, “What business do we have with each other, Jesus, Son of the Most High God? I beg You, do not torment me.” 
Luke 8:29  For He had commanded the unclean spirit to come out of the man. For it had seized him many times; and he was bound with chains and shackles and kept under guard, and yet he would break his bonds and be driven by the demon into the desert. 
Luke 8:30  And Jesus asked him, “What is your name?” And he said, “Legion”; for many demons had entered him. 
Luke 8:31  They were imploring Him not to command them to go away into  the abyss. 

Jesus asked the name of the demon horde, and they responding with the name “Legion.” Jesus then proceeded in casting out the entire group. This was the only process of exorcism known to men in Israel, and the key to the process was learning the demon’s name.

Therefore, if a possessed person was mute (i.e., unable to speak), then an exorcism was impossible. Without the ability to learn the demon’s name, a priest would be unable to perform the exorcism as prescribed. As a result of this limitation, a teaching arose among religious leaders in Israel that only the true Messiah could cast out a demon from a mute person.

We see this tradition reflected in another story of demon possession found in Mark’s Gospel:

Mark 9:17  And one of the crowd answered Him, “Teacher, I brought You my son, possessed with a spirit which makes him mute; 
Mark 9:18  and  whenever it seizes him, it  slams him to the ground and he foams at the mouth, and grinds his teeth and  stiffens out. I told Your disciples to cast it out, and they could not do it.” 
Mark 9:19  And He answered them and said, “O unbelieving generation, how long shall I be with you? How long shall I put up with you? Bring him to Me!”
Mark 9:20 They brought the boy to Him. When he saw Him, immediately the spirit threw him into a convulsion, and falling to the ground, he began rolling around and foaming at the mouth.
Mark 9:21  And He asked his father, “How long has this been happening to him?” And he said, “From childhood. 
Mark 9:22  “It has often thrown him both into the fire and into the water to destroy him. But if You can do anything, take pity on us and help us!” 
Mark 9:23  And Jesus said to him, “‘If You can?’ All things are possible to him who believes.”
Mark 9:24  Immediately the boy’s father cried out and said, “I do believe; help my unbelief.” 
Mark 9:25  When Jesus saw that a crowd was rapidly gathering, He rebuked the unclean spirit, saying to it, “You deaf and mute spirit, I command you, come out of him and do not enter him again.”
Mark 9:26  After crying out and throwing him into terrible convulsions, it came out; and the boy became so much like a corpse that most of them said, “He is dead!” 
Mark 9:27  But Jesus took him by the hand and raised him; and he got up. 
Mark 9:28  When He came into the house, His disciples began questioning Him privately, “Why could we not drive it out?” 
Mark 9:29  And He said to them, “This kind cannot come out by anything but prayer.”

Jesus encountered a young boy possessed by a demon. As we read, the demon had rendered the boy mute, which is the key detail in this story. The boy’s father is especially troubled, because he knows that no ordinary man could heal his son in his mute condition. Since no man can learn the name of the demon, there is no hope for an exorcism. As we see, the disciples attempted to cast out the demon, but failed because they could not obtain the demon’s name.

Consequently, the father brought his son to Jesus for healing, probably because the father knew Jesus was the Messiah, and therefore he expected that Jesus could overcome this barrier. When Jesus remarked, “O unbelieving generation, how long shall I be with you?” He was referring to His disciples, who had tried in vain to cast out the demon. If His disciples truly understood Jesus was the Messiah, they would have known to bring the boy to Him instead of tryhing perform a feat reserved only for the Messiah. Jesus was highlighting their continuing unbelief in His Messiahship. 

After Jesus finished healing the boy, His disciples questioned Him as to why He was able to perform this miracle yet they could not. Jesus answered by saying this “kind” of demon possession only comes out with prayer and fasting. In other words, only God can remove a demon from a mute body, which is why this miracle is a sign of the Messiah. Therefore, the disciples’ only recourse was to appeal to God through prayer and fasting for a deliverance.

With that background, we return to our passage in Matthew to find Jesus casting out another mute demon. After Jesus heals the man, the Jewish crowd correctly realizes they just witnessed one of the Messianic miracles. Notice in Matt 12:23 the crowd exclaims, "This man cannot be the Son of David, can he?” The term “son of David” is a Messianic term, so the crowd is asking themselves if it is true that Jesus is their long-awaited Messiah. By the tone of their question, we can see they doubted in their own conclusion, because Jesus did not fulfill their expectations for who would be the Messiah. 

So the crowd waited for their religious leaders, the Pharisees, to rule on their question. Was Jesus truly the Messiah as the miracle indicated? Rather than acknowledging the obvious and declaring Jesus to be the Messiah, the hard-hearted Pharisees concocted an alternative answer to explain away Jesus' extraordinary miracle. In v.24 they attribute His miracle to the power of Satan (Beelzebul). Their explanation was illogical and absurd, as Jesus’ rebuke points out in vs.25-30.

Nevertheless, the people in the crowd agreed with the Pharisees' assessment. Rather than accepting Jesus as their Messiah, the crowd followed the lies of their religious leaders, choosing to believe Jesus was acting with the power of Satan. Their decision to attribute Jesus' miraculous power to Satan instead of to the Holy Spirit is the sin of blaspheming the Holy Spirit.

The people of Israel witnessed the power of the Holy Spirit working to confirm Jesus as Messiah, and even though they correctly declared it to be a sign of the Messiah, they blasphemed the Holy Spirit by declaring the miracle was the work of Satan. In a sense, they were confessing that Satan was lord, rather than confessing Jesus as Lord. This is an unforgivable sin, according to Jesus.
 

Just the sin of unbelief?
 

A common (mis)interpretation of the unpardonable sin suggests that Jesus was speaking merely about the sin of unbelief (i.e., dying without accepting Christ as Lord), but the context of Jesus' words and the related scriptures leads us to reject this interpretation. 

First, Jesus called this special sin "blaspheming the Holy Spirit," and He assigned it an unique penalty unlike any other sin:

Matt. 12:31  “Therefore I say to you, any sin and blasphemy shall be forgiven people, but blasphemy against the Spirit shall not be forgiven.
Matt. 12:32 “ Whoever speaks a word against the Son of Man, it shall be forgiven him; but whoever speaks against the Holy Spirit, it shall not be forgiven him, either in this age or in the age to come.

Notice Jesus says that speaking against Christ is forgivable, while blaspheming the Holy Spirit is not forgivable. Rejecting the Gospel is a rejection of Christ, yet Jesus specifically says this sin can be forgiven. On the other hand, blaspheming the Holy Spirit offers no possibility of forgiveness, “...either in this age or in the age to come” Jesus says.

The word age refers to our present time on earth, while the "age to come" refers to the eternal age. Jesus says that once the unforgivable sins occurs, there can be no forgiveness in this age. In other words, once this sin occurs, a person is precluded from forgiveness even while they still live in the present age. 

Based on this penalty, we know Jesus cannot be speaking about rejecting Christ. If someone rejects Christ today, that person can still receive forgiveness at a later point in this age should the person accept the Gospel on a future day. A person who rejects Christ a million times is still eligible for forgiveness “in this age” until they die. This fact explains why Jesus says speaking "against the Son" is forgivable in this age. Rejecting Christ can be forgiven in this age, so long as the person repents before the age is over (i.e., before death).

On the other hand, blaspheming the Holy Spirit offers no such second chance. Jesus says that when the unforgivable sin is committed, it shall not be forgiven in this age. When this sin is committed, it eliminates all future opportunity for forgiveness even while a person is still alive. There is no second chance for those who commit this particular sin. This unique penalty means Jesus was speaking about something very different than merely rejecting the Gospel. 

Jesus was speaking about the unique circumstances Israel encountered when they rejected Christ face-to-face. Israel committed the unpardonable sin, and therefore that entire generation of Israel received a special judgment - a judgment that only that generation could experience. Their penalty was disqualification from receiving the Kingdom. Instead of receiving the Kingdom, that generation was excluded forever from God's forgiveness, leaving only a remnant of Israel to know Christ and receive the Kingdom. The rest of Israel was hardened, according to Paul:

Rom. 11:7  What then? What Israel is seeking, it has not obtained, but those who were chosen obtained it, and the rest were hardened; 
Rom. 11:8  just as it is written,
                   “GOD GAVE THEM A SPIRIT OF STUPOR,
                   EYES TO SEE NOT AND EARS TO HEAR NOT, 
                    DOWN TO THIS VERY DAY.” 
Rom. 11:9   And David says, 
                   “LET THEIR TABLE BECOME A SNARE AND A TRAP,
                    AND A STUMBLING BLOCK AND A RETRIBUTION TO THEM. 
Rom. 11:10  “LET THEIR EYES BE DARKENED TO SEE NOT, 
                     AND BEND THEIR BACKS FOREVER.” 
 

A few verses later in Matt 12, Jesus revealed this judgment upon this generation of Israel because they committed the unforgivable sin:

Matt. 12:39  But He answered and said to them, “An evil and adulterous generation craves for a sign; and yet no sign will be given to it but the sign of Jonah the prophet;
Matt. 12:40  for just as JONAH WAS THREE DAYS AND THREE NIGHTS IN THE BELLY OF THE SEA MONSTER, so will the Son of Man be three days and three nights in the heart of the earth.
Matt. 12:41 “The men of Nineveh will stand up with this generation at the judgment, and will condemn it because they repented at the preaching of Jonah; and behold,  something greater than Jonah is here.
Matt. 12:42  “The Queen of the South will rise up with this generation at the judgment and will condemn it, because she came from the ends of the earth to hear the wisdom of Solomon; and behold, something greater than Solomon is here.

That generation of Israel was condemned for the remainder of their earthly lives and into eternity, Jesus declares. No second chances. No reprieve. Not in this age nor the next. And notice the reason Jesus gives for why this generation's unbelief was unforgivable when past generations of Israel were permitted to repent and did receive forgiveness for their unbelief: because this time “something greater is here.”

In other words, Jesus says that because this generation of Israel saw the Messiah in person, they could not be forgiven for rejecting Him. A person can be forgiven through repentance and faith for rejecting lessor messengers who declare the Gospel (i.e., the apostles, evangelists, prophets, etc.), but there is no second chance for a person who rejects Jesus to His face. By blaspheming the Holy Spirit in the physical presence of the Messiah, Israel committed a unique sin that could not be forgiven that generation.

We can see even more confirmation of this unique and pivotal moment in Israel’s history by noticing how Jesus’ teaching changed immediately after Israel committed the unpardonable sin. Prior to the unpardonable sin (in Matt 1-12), Jesus never taught a single parable. Everything He taught was in the open for all to hear and understand.

But after Israel committed the unpardonable sin in Matt 12, Jesus changed His teaching style dramatically. From Matthew 13 until His death on the cross, Jesus only taught in parables. After the unpardonable sin, Jesus begins hiding the truth from Israel, because Israel is no longer permitted to understand it, because they cannot be forgiven. 

Even the disciples noticed Jesus' abrupt change in style, so they ask Jesus in Matthew 13 why He has suddenly begun to teach in parables. Look at what Jesus says in response:

Matt. 13:10  And the disciples came and said to Him, “Why do You speak to them in parables?” 
Matt. 13:11  Jesus answered them, “To you it has been granted to know the mysteries of the kingdom of heaven, but to them it has not been granted.
Matt. 13:12  “For whoever has, to him more shall be given, and he will have an abundance; but whoever does not have, even what he has shall be taken away from him.
Matt. 13:13  “Therefore I speak to them in parables; because while seeing they do not see, and while hearing they do not hear, nor do they understand.
Matt. 13:14  “In their case the prophecy of Isaiah is being fulfilled, which says, 
                      ‘YOU WILL KEEP ON HEARING, BUT WILL NOT UNDERSTAND; 
                       YOU WILL KEEP ON SEEING, BUT WILL NOT PERCEIVE;
Matt. 13:15    FOR THE HEART OF THIS PEOPLE HAS BECOME DULL, 
                      WITH THEIR EARS THEY SCARCELY HEAR, 
                       AND THEY HAVE CLOSED THEIR EYES, 
                       OTHERWISE THEY WOULD SEE WITH THEIR EYES, 
                      HEAR WITH THEIR EARS, 
                      AND UNDERSTAND WITH THEIR HEART AND RETURN, 
                      AND I WOULD HEAL THEM.’
Matt. 13:16  “But blessed are your eyes, because they see; and your ears, because they hear.

Jesus says that only a few in Israel (the remnant) would be permitted from this point forward to know the truth. Just as the OT prophets foretold, Israel would not be permitted to understand the truth of the Messiah as a judgment against them. Notice in Matt 13:15, Isaiah declared that God has closed Israel's eyes and ears so that they could not hear or understand. In other words, their sin would not be forgiven in this age.

Finally, we see even more confirmation that Israel’s sin was unforgivable in another passage:

Luke 13:34 “O Jerusalem, Jerusalem, the city that kills the prophets and stones those sent to her! How often I wanted to gather your children together,  just as a hen gathers her brood under her wings, and you would not have it!
Luke 13:35 “Behold, your house is left to you desolate; and I say to you, you will not see Me until the time comes when you say, ‘ BLESSED IS HE WHO COMES IN THE NAME OF THE LORD!’”

Here Jesus pronounce Israel's final judgment for unbelief. Notice Jesus says Israel’s “house” is left to them desolate (from that point forward). This moment occurred only shortly after the events in Matt 12, so Jesus made this declaration long before He was crucified and long before the Romans destroyed the city. He pronounced Israel's judgment here in Luke 13 while there was yet still time for the nation to receive Him as Messiah. 

Why did Jesus declare judgment upon Israel for unbelief at such an early point in His earthly ministry? Because Israel's die was cast once they committed the unforgivable sin. There could be no forgiveness "in this age" (as Jesus said) for the unforgivable sin, so from this point onward, this generation of Israel was under judgment.

Notice also Jesus declares that Israel will not see their Messiah and the Kingdom “until" a future generation of Israel reverses the sin of this generation by declaring Jesus to be Lord. A future generation of Israel must reverse the sin of this generation by confessing that Jesus is Messiah, and when the nation follows suit, then (and only then) Jesus will return to set up the promised Kingdom. In other words, the Lord’s Second Coming hinges on the entire nation of Israel declaring “Blessed is He Who comes in the name of the Lord" (i.e., declaring that Jesus is Messiah). 

Israel will finally meet these terms on the last day of Tribulation (according to Zech 12-14), resulting in the return of Christ:

Zech. 12:9 “And in that day I will   set about to destroy all the nations that come against Jerusalem. 
Zech. 12:10  “I will  pour out on the house of David and on the inhabitants of Jerusalem, the Spirit of grace and of supplication, so that they will look on Me whom they have  pierced; and they will mourn for Him, as one  mourns for an only son, and they will weep bitterly over Him like the bitter weeping over a firstborn. 
Zech. 12:11 “In that day there will be great  mourning in Jerusalem, like the mourning of Hadadrimmon in the plain of  Megiddo. 
Zech. 12:12 “The land will mourn, every family by itself; the family of the house of David by itself and their wives by themselves; the family of the house of Nathan by itself and their wives by themselves; 
Zech. 12:13 the family of the house of Levi by itself and their wives by themselves; the family of the Shimeites by itself and their wives by themselves; 
Zech. 12:14 all the families that remain, every family by itself and their wives by themselves. 

Zech. 14:2 For I will  gather all the nations against Jerusalem to battle, and the city will be captured, the  houses plundered, the women ravished and half of the city exiled, but the rest of the people will not be cut off from the city. 
Zech. 14:3 Then the LORD will go forth and  fight against those nations, as  when He fights on a day of battle. 
Zech. 14:4 In that day His feet will  stand on the Mount of Olives, which is in front of Jerusalem on the east; and the Mount of Olives will be  split in its middle from east to west by a very large valley, so that half of the mountain will move toward the north and the other half toward the south. 

When the Lord pours out His Spirit on Israel at the end of Tribulation, the nation will respond with a mass confession of faith in Christ. Once all Israel has made this declaration, then Christ will return to defeat the antichrist and set up the Kingdom for Israel (as He promised in Luke 13).

So the unpardonable sin is closely related to the Second Coming of Christ. It’s no “ordinary” rejection of the Gospel. It is the very reason Jesus left the earth the first time!