As a pastor I’ve been asked the question with some regularity, usually by a young person, “Is there a sin that can’t be forgiven?” In fact, the question was posed to me recently by one of our youth at CoJ. The question is most often provoked by a study of either Mark 3:28-29, where Jesus says, “I tell you the truth, all the sins and blasphemies of men will be forgiven them. But whoever blasphemes against the Holy Spirit will never be forgiven; he is guilty of an eternal sin;” or Matthew 12:31-32, which similarly says – “And so I tell you, every sin and blasphemy will be forgiven men, but the blasphemy against the Spirit will not be forgiven. Anyone who speaks a word against the Son of Man will be forgiven, but anyone who speaks against the Holy Spirit will not be forgiven, either in this age or in the age to come.”
In my experience, youth seem particularly vulnerable to the thought that there likely is a particular sin that is so heinous that God just can’t or won’t forgive it, and moreover, that it’s quite possible he or she (or a close friend) has already committed it.
First of all, to this I say that the Scripture passages cited above have a particular context in mind – Jesus’ exchange with the Pharisees, 
a sect of the Jews of His day, who strictly adhered to the Law of Moses and were proud of their ability to do so. The Pharisees had made the assertion that Jesus’ popularity and miraculous works were the result of Satan’s influence in His life. Jesus called this, “the blasphemy against the Holy Spirit,” or attributing the work of God to the devil, a serious offense with the gravest possible consequences, according to Jesus. Yet, as we search the Scripture, there are numerous forms of serious sins committed by a wide assortment of people that God seems willing and able to forgive. Why does Jesus single out this sin? What is meant by “the blasphemy against the Holy Spirit,” which Jesus asserts is “unforgivable?”
When all is said and done, scriptural analysis yields one, clear conclusion – that the only unforgivable sin is chronic unbelief, from which at some point no future repentance is possible. After all, it is the Holy Spirit working through the the Word that shows people their sins, leads them to repentance, and enables them to believe the gospel of Jesus Christ. A person who hears the call of the gospel, but who repeatedly hardens his heart and refuses to repent and believe, at some point will become permanently resistant – which is the ultimate sin against the Holy Spirit. I must hasten to add that it is not ours to determine at what point a person becomes permanently resistant to the call of the Gospel. This knowledge belongs to God. John 3:36 sums it up well, saying – “Whoever believes in the Son has eternal life, but whoever rejects the Son will not see life, for God’s wrath remains on him.”
In conclusion, there is something I’d like to say to anyone who is deeply troubled by a guilty conscience in fear that they have sinned too deeply for God to forgive them, or who is seeking to help someone else in that situation: God’s ability to save is not limited by our sinfulness. In fact, outside of a relationship with
Jesus Christ, we are all in total rebellion against God, even though some people seem to be worse sinners than others. I John 2:1-2 says, “… if anybody does sin, we have one who speaks to the Father in our defense – Jesus Christ, the Righteous One. He is the atoning sacrifice for our sins, and not only for ours but also for the sins of the whole world.” In other words, Jesus has died for all sinners. The “sins of the whole world” have been paid for at the cross of Calvary. For you whose conscience is bothering you, God’s Word affirms that forgiveness is possible. The very fact that you are bothered by your sin shows that the Holy Spirit has not abandoned you and that God has not given up on you. In fact, if you have truly received Jesus Christ as your Savior, you can’t commit a sin for which there is no forgiveness. As stated in Romans 8:1 – “Therefore, there is now no condemnation for those who are in Christ Jesus, ….” Take comfort in these words. – MAJ