Question: I'm worried that I may have committed blasphemy of the Holy Spirit. How can I know if I committed this sin?
Jesus said, "Truly I say to you, all sins shall 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 "-because they were saying, "He has an unclean spirit." (Mark 3:28-30)
The scribes committed blasphemy when they attributed the miracles of Jesus to the devil instead of the Holy Spirit. They accused Jesus of being possessed by the devil and casting out demons by the power of Satan (Mark 3:22).
Some Bible scholars believe that this particular sin could only be committed while Christ was on earth because the scribes said that Jesus was possessed by Satan. They witnessed with their own eyes the perfect Son of God performing miracles by the Spirit of God. In other words, this sin can't be duplicated today simply because Jesus is no longer on earth in His physical body. The reason Jesus gave this warning was "because they were saying, 'He (Jesus) has an unclean spirit.'"
Many people are afraid that they may have committed the unpardonable sin. The scribes were so embittered and hardened of heart that they weren't the least bit concerned about their own spiritual condition. The fact that you are concerned that you may have blasphemed the Holy Spirit is proof that you have NOT committed this sin. A person who could commit the unpardonable sin wouldn't care.
If you are unsure of your salvation, please see our study "How can I know I'm going to heaven?"