What is blaspheming against the Holy Spirit, and how can any sin be unforgivable?
As further context for this question, might we first look at the passage from Mark 3:22-30, within which Jesus makes reference to these matters of
blaspheming against the Holy Spirit:
“The scribes who had come from Jerusalem said, ‘He is possessed by Beelzebul,’ and ‘By the prince of demons he drives out demons.’ Summoning them, he began to speak to them in parables, ‘How can Satan drive 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; that is the end of him. But no one can enter a strong man’s house to plunder his property unless he first ties up the strong man. Then he can plunder his house. Amen, I say to you, all sins and all blasphemies that people utter will be forgiven them. But whoever blasphemes against the Holy Spirit will never have forgiveness, but is guilty of an everlasting sin.’ For they had said, ‘He has an unclean spirit.’”
In this passage, clearly Jesus is addressing the fact that any detraction or false statement against the power of the Holy Spirit (such as to say that it is “unclean”) is a blasphemy against the Holy Spirit. To utter such blasphemy is to both offend against the truth of God and the Holy Spirit and to deny the power of the Holy Spirit as life, love, forgiveness, healing, etc. Such denial cannot be forgiven insofar as it is a denial of He who forgives – it is in direct contradiction and therefore cannot be reconciled. Said another way, one cannot be forgiven if they renounce the power by which they would otherwise be forgiven.
What must be rightly understood, however, is that such a sin as a blasphemy (as with any sin) can be repented of, so that having repented one may be forgiven. In other words, if a person who uttered a blasphemy repents of it, acknowledging before God that they were wrong in stating such and then subsequently expresses faith, turning toward God, acknowledging the power of the Holy Spirit, they can be forgiven of this and every other sin. Simply put, it is a matter of fully accepting in faith the truth of the Holy Spirit versus a denial of such. All who accept the truth can be forgiven; any who deny its power cannot (of their own word) receive what they have denied.