Much has been written and said concerning the episode covered by Matthew, Mark and Luke on one occasion of Jesus healing those who had evil spirits tormenting them. In Matthew’s account, Jesus encountered a man in which was a demon that caused him to be unable to see or to speak. When Jesus cast out the demon and the man began to speak and see, some of those seeing it, began to believe on Jesus and made the remark, “Is this the son of David?” which meant the messiah. We need to read Mark’s account here of what occurred.
And the scribes who came down from Jerusalem said, "He is possessed by Be-el'zebul, and by the prince of demons he casts out the demons." And he called them to him, and said to them in parables, "How can Satan cast out Satan? If a kingdom is divided against itself, that kingdom cannot stand. And if a house is divided against itself, that house will not be able to stand. And if Satan has risen up against himself and is divided, he cannot stand, but is coming to an end. But no one can enter a strong man's house and plunder his goods, unless he first binds the strong man; then indeed he may plunder his house. "Truly, I say to you, all sins will be forgiven the sons of men, and whatever blasphemies they utter; but whoever blasphemes against the Holy Spirit never has forgiveness, but is guilty of an eternal sin" -- for they had said, "He has an unclean spirit." (Mark 3:22-30 NASV)
We have purposely posted the NASV of the scripture above in order for the verbs to be seen accurately. It is important to understand this since it holds the answer to our inquiry of the matter. They used the imperfect tense of their verbs, inferring that Jesus was continuously performing these miracles by the power of Beelzebub (Satan).
What it actually shows is that they knew he was doing this via the Holy Spirit but were denying it anyway. So it was not that they were mistaken, they knew better. And even though they were witnessing the works of the Holy Spirit and knew full well where the power was from, they were willfully denying and ridiculing it.
When one’s heart is so determined to have nothing to do with God or His works, there is nothing which will change them. An honest heart, such as Paul of Tarsus, even though he was persecuting the church of Christ and blaspheming the works of the Holy Spirit, was honest and his heart was determined to work for the true God. When he learned of his error, he repented and was forgiven of his blasphemy.
But the Pharisees above, knew full well they were blaspheming the Holy Spirit. There is no return from that depth of sin.
Many say that today we cannot commit this sin since we are not being eyewitnesses to the miracles of Jesus. Hold on. Jesus, the apostles and those selected by them could perform these miracles by the power of the Holy Spirit, in order to confirm the word. Today, Christians have the complete word of God at their fingertips. The people did not have it all at that time. The miracles are recorded for us and it is a direct command that we accept this word. If, we have it available and still deny and blaspheme the Bible, Jesus, the Holy Spirit and/or God, we are without excuse.
The world is full of such, many of whom spend their days striving to prove the Bible to be uninspired. These are the ones whom Jesus refers to by “Truly, I say to you, all sins will be forgiven the sons of men, and whatever blasphemies they utter; but whoever blasphemes against the Holy Spirit never has forgiveness, but is guilty of an eternal sin” (Mark 3:28-29 NASV)