Verily I say unto you, All sins shall be forgiven unto the sons of men, and blasphemies wherewith soever they shall blaspheme: But he that shall blaspheme against the Holy Ghost hath never forgiveness, but is in danger of eternal damnation: Mark 3:28-29

There is one sin that Jesus said he will not forgive “Blasphemy of the Holy Spirit”, this should obviously be a dire warning to everyone, God will not be mocked. So the obvious question is “What is blasphemy of the Holy Spirit”?  The dictionary defines Blasphemy as “ Act of insulting , showing contempt, or lack of reverence towards God” or “Acting or claiming the attributes of a deity”

I think it’s interesting because in this statement, Jesus is basically declaring that the Holy Spirit is God. If the Holy Spirit wasn’t God, then blaspheming against him wouldn’t really be a sin. Notice the punishment, eternal damnation, Hell. 

When you understand that we are dead in our sins (Ephesians 2) its the Holy Spirit that convicts us of our sin and leads us to Christ. If you reject this conviction or calling , this would be one example of blasphemy of the Holy Spirit. Many of the religious leaders knew the scriptures, they witnessed the miracles performed by Christ, yet they still rejected him, they rejected the Holy Spirit, which leads to eternal damnation

Because they said, He hath an unclean spirit. Mark 3:30

Notice Jesus charged the religious leaders with blasphemy because they accused him of being possessed with demons. Again this displays that Jesus is God also, if Jesus wasn’t God, then it really wouldn’t be blasphemy. But because God is Triune, Father , Son , and Holy Spirit, any rejection of the three is blasphemy and eternal damnation

Why did religious leaders reject Christ? Was it due to lack of evidence, no? Was it due to their lack of knowledge with scripture?, No, It was because they have hardened their hearts and loved their religion more than they loved the true living God. They made an idol out of their traditions and statuses, and rejected the calling of the Holy Spirit

Many even today have rejected the Holy Spirit, they claim not to know God or understand his direct revelation. But God knows their hearts, God knows their thoughts, God knows they have committed blasphemy of the Holy Spirit and will be eternal damned!