Blasphemy Against the Holy Spirit
Then a demon possessed man who was blind and mute brought to him, and he called him, so that the man spoke and saw. And all the other people were amazed, and said, "can this be the Son of David?" But when the Pharisees heard it, they said, "It is only by Belzebel, the prince of demons, that this man casts out demons." Knowing their thoughts, he said to them, "Every kingdom divided against itself is laid waste, and no city or house divided against itself will stand. And if satan casts out satan, he is divided against himself. How then will his kingdom stand? And if I cast out demons by Beelzebul, by whom do your sons cast them out? Therefore they will be your judges. But if it is by the Spirit of God that I cast out demons, then the "kingdom of God that comes upon you, or how can someone enter a strong man's house and plunder his goods, unless he first binds the strong man? Then indeed he may plunder his house. Whoever is not with me is against me, and whoever does not gather with me scatters. Therefore I tell you, every sin and blasphemy will be forgiven people, but the blasphemy against the Holy Spirit will not be forgiven. And whoever speaks a word against the Son of Man will be forgiven, but whoever speaks against the Holy Spirit will not be forgiven, either in this age and the age to come.
Study: (Matthew 12:31-32)
Blasphemy against the Spirit will not be forgiven. The sin is attributing to satan what is accomplished by the power of God, and doing this through the flagrant, willful, and persistent rejection of God and His commands. This sin is committed today only by unbelievers who deliberately and unchangeably reject the ministry of the Holy Spirit in calling them to salvation.
~ESV Study Bible~