Insulting the Holy Spirit
I read in the Bible three things that people are doing to the Holy Spirit. First of all, in Ephesians 4:30: "And grieve not the holy Spirit of God, whereby ye are sealed unto the day of redemption." Notice that people can grieve the Holy Spirit, and the Bible says it will be done in these last days.
What else will they do to God's personal representative? In Hebrews 10:29 we are told that men will despise the Holy Spirit. "Of how much sorer punishment, suppose ye, shall he be thought worthy, who hath trodden under foot the Son of God, and hath counted the blood of the covenant, wherewith he was sanctified, an unholy thing, and hath done despite unto the Spirit of grace?" That word "despite" means the same as despise. Just think of it! They will despise the Holy Spirit. And then let's get one other thing before us. This is in Acts 7:51: "Ye stiff necked and uncircumcised in heart and ears, ye do always resist the Holy Ghost: as your fathers did, so do ye." So there we have three things that men will do to insult the Spirit of God: they grieve, they despise, and they resist Him just as they did back in the days of Noah.
What effect does all this rebellion against the Spirit have upon the person who does it? Almost imperceptibly the conscience is seared and the heart is hardened. In fact, this is why it is counted such a terrible sin. Sometimes people say, "I don't understand why God should consider this the worst thing that can be done." I'll tell you why: because the Holy Spirit is the only way God can reach an individual. There is no other way for God to save a person except through the Holy Spirit. That is the way we are led to repentance. If we do not have the Holy Spirit, there is no hope for us.
It's like a man out in the sea who is drowning alone, and somebody throws one life preserver to him. If the man will lay hold of that life preserver, he can be saved, but if he refuses to take hold of the only link to the shore, he will perish without hope. In the same way, we are in this world, and the only way God can reach us is by the Holy Spirit. If we turn away from that Spirit and refuse to listen and obey, God will have to let us go and be lost. This is why David was so deeply concerned in his great prayer of contrition. While pouring out his heart to God in Psalm 51, David said, "Cast me not away from thy presence; and take not thy holy spirit from me" (verse 11). He realized that if God removed the Holy Spirit, he was lost. He would be left alone with no way of being saved. And that's why Jesus said that it's the unpardonable sin. When you cut yourself off and refuse to listen to the Holy Spirit, there is no hope for you.