Question: : What is the “unforgivable sin” and “the blasphemy against the Holy Spirit”?
Answer: When Jesus heals a certain demonized man who is both blind and mute, the Pharisees say he had authority over the demons because he cast them out by the prince of demons (Matthew 12:22-37). In other words, they accuse him of being in league with Satan and using Satan’s power to cast out demons as a way of tricking people into believing in him. Jesus argues that Satan would thus be dividing his own kingdom against itself and this strategy would lead to his destruction. He claims instead that his power has come from the Spirit of God.
But because the Pharisees have attributed the Spirit’s power working through him to Satan instead, they have blasphemed (spoken evil against) the Holy Spirit. Every indicator in the miracles that Jesus performed pointed to the fact that it was the Holy Spirit and not Satan who was behind Jesus’ miracles. The Pharisees were responsible as leaders of Israel to evaluate any contenders to messiahship. But if they had not had a personal agenda of retaining their own power and influence, they could instead have acknowledged that Jesus’ compassion, the sheer number of miracles, the good results coming from them of people giving God glory, and their changed lives proved that God was behind Jesus’ ministry.
Instead they hardened their hearts against the truth and attributed to Satan what only the Holy Spirit could have done. Consequently, Jesus said their sin would not be forgiven in this age or the age to come, that is, ever. The unforgivable or unpardonable sin is refusing to see the plain truth in front of you of the Holy Spirit’s power and attestation that Jesus is the Messiah. Anyone who is blessed to see the truth this plainly but hardens his or her heart to it and refuses to submit to the truth cannot be forgiven.
If someone you think might have committed the unpardonable sin does demonstrate repentance and faith, you know they did not commit the unpardonable sin, or else they would not be able to have repentance and faith. If someone wants Jesus in his or her life, they can have him. The fact they want him shows they did not commit the unpardonable sin.