What is meant by blaspheming the Holy Spirit (the third Person of the Trinity)?
After Jesus performed many miracles, healed the sick, and taught people to do good and stay away from wickedness, some of the scribes and Pharisees accused Jesus of being demon possessed. So Jesus spoke against them, saying that anyone who blasphemes against the Spirit of God (Holy Spirit) is guilty forever.
“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)
Blaspheming the Holy Spirit: a deliberate sin
Blaspheming the Holy Spirit is a deliberate sin, not one made casually. It is also not something that is done by accident, or something that is not meant by the person committing it. The scribes in Jesus’s day came from Jerusalem and said on purpose, “He casts out the demons by the ruler of the demons” (Mark 3:22).
So they were not only saying these things against Jesus, but they were saying these things against the Holy Spirit who dwells in Jesus and by whose power Jesus casts out demons.
Anyone who says these things, deliberately and willfully accuses the Holy Spirit of being evil. Such a person reviles the Spirit of Truth. This person also cannot receive the Spirit of God who gives eternal life, because he hates Him.
Jesus said, “I will ask the Father, and He will give you another Helper, that He may be with you forever; that is the Spirit of truth, whom the world cannot receive, because it does not see Him or know Him, but you know Him because He abides with you and will be in you” (John 14:16-17).
So the Holy Spirit dwells in believers, but the world does not know Him.
“In Him, you also, after listening to the message of truth, the gospel of your salvation—having also believed, you were sealed in Him with the Holy Spirit of promise, who is given as a pledge of our inheritance, with a view to the redemption of God’s own possession, to the praise of His glory.” (Ephesians 1:13-14)
Since the Spirit of God is given to believers as a pledge, those without the Spirit of God does not belong to Christ (Romans 8:9). And if the world cannot receive God’s Spirit and is judged for refusing Christ, how much more would a person be judged, if he not only doesn’t receive the Holy Spirit of promise by believing in Jesus, but accuses the Spirit of God of being evil?
Do not be fooled
If you’re not a believer, do not attempt to commit this sin by blaspheming the Holy Spirit. Do not be fooled into doing this. You do not know what will happen in the future. Why should you cut off from yourself any possibility of a lifeline?
Trust God to keep you from all evil
Christians, by believing in Christ you recognize Jesus as Lord and coming from the Father. You know that the Holy Spirit given to you to help you is within you and is from God.
If you are a believer, “do not grieve the Holy Spirit of God, by whom you were sealed for the day of redemption” (Ephesians 4:30). Walk in God’s ways, rest in the Holy Spirit, and trust God to keep you from sin. God will keep your feet from slipping and protect you from falling.
“My help comes from the Lord,
Who made heaven and earth.
He will not allow your foot to slip;
He who keeps you will not slumber….
The Lord will protect you from all evil;
He will keep your soul.” (Psalm 121: 2-3,7)
Take comfort in the fact that God cares for you, and “He Himself has said, ‘I will never desert you, nor will I ever forsake you'” (Hebrews 13:5).
Read Mark 3 in the Bible.
To learn more about the Holy Spirit, see this article on the Holy Spirit.