“Therefore I say to you, any sin and blasphemy shall be forgiven men, but blasphemy against the Spirit shall not be forgiven. And whoever shall speak a word against the Son of Man, it shall be forgiven him; but whoever shall speak against the Holy Spirit, it shall not be forgiven him, either in this age, or in the age to come” (Matthew 12:31, 32).
At one point in His ministry, the Pharisees accused Jesus of performing His miracles by the power of Beelzebul, a ruling territorial spirit. In response, Jesus said that if He were casting out demons by the power of Beelzebul, then Satan would be casting out Satan. Satan would be divided against himself, and his kingdom could not stand. Jesus then explained that, since He was casting out demons by the Spirit of God, the kingdom of God had come upon them (see Matthew 12:28). Clearly, they were rejecting the Spirit of God by crediting His work to Beelzebul.
So why did Jesus say that a person can speak against Him, but not the Holy Spirit? The answer to this question comes with understanding that the unique role of the Holy Spirit was and is to give evidence to the work of Christ and to lead us into all truth (see John 14:17-19; 16:7-15). The only unpardonable sin is the sin of unbelief. If we refuse to accept the testimony given to us by the Holy Spirit, fight off His conviction of our sin, and never accept the truth, we will never come to Christ for salvation. In Christ, all our sins are forgiven. Therefore, no Christian can commit the unpardonable sin. Only an unregenerate person who refuses to come to Christ will die in his or her sins.
The accuser of the brethren, however, will often try to convince Christians that they have committed the unpardonable sin so that they will live in defeat. We encourage you to read Living Free in Christ, which was written to help Christians understand their relationship with God and their identity in Christ so that they can stand against such lies of our adversary. Even as Christians, however, we can quench the Spirit. If we do, we will impede the work of God and live a less than victorious life, but we will not lose our salvation.