We often hear people say that they are afraid they have committed the unpardonable sin and that is the reason why they cannot say they know they are saved. When they are asked, "What is the unpardonable sin?" they say they do not know, but they feel they have committed it whatever it may be.
The Bible would not tell us that there is an unpardonable sin without telling us what that sin is. Matthew 12:32, Mark 3:28,29 and Luke 12:10 definitely tell us (and these are the words of the Son of God) that blasphemy against the Son of Man will be forgiven, but blasphemy against the Holy Spirit of God will not be forgiven either in this world or in the world to come. How then could this be that one may be forgiven for blasphemy against Christ, but not forgiven for blaspheming against the Holy Spirit. The reason is that each one of the Triune God performs a different part in the great plan of the Salvation of Mankind. The Father loved the world and freely gave His Son as a sacrifice for sin. The Son (Jesus Christ, our Lord) willingly died and gave His life a ransom for all on Calvary's cruel cross, but the Spirit of God Who came into the world when Christ returned to Glory is here to convince men of sin and lead them to believe on Christ and be saved.
It is not that the Spirit of God occupies a higher place in the Godhead (for God the Father, God the Son and God the Holy Spirit are equal, three in one) but it is the work that the Holy Spirit is doing which makes it so important for all not to refuse nor resist His work in their hearts and souls in this the Day of God's Grace.
Man being created a "free moral agent" is wholly responsible for what he believes and what he refuses to believe; therefore, the sacrifice of Christ does not provide pardon for "unbelief", and unbelief becomes the unpardonable sin. John 3:18 is very definite and distinctly states, "He that believeth on Him (Christ) is not condemned, but he that believeth not is condemned already because he has not believed on the Name of the only begotten Son of God." The work of the Holy Spirit is to regenerate everyone who believes on Christ and to make him a new creation in Christ Jesus the very moment he believes. But if he resists the strivings of the Holy Spirit within him and chooses to remain in unbelief, the Bible states he is trampling under foot the Son of God and is counting the blood of the covenant wherewith he was sanctified an unholy thing and is doing despite unto the Spirit of grace. Hebrews 10:29.
"Today if you will hear His voice harden not your heart." (Hebrews 3:15). Tomorrow may be too late. ( Proverbs 27:1).
God cannot save an unbeliever. "He that believeth not shall be damned." Mark 16:16.
Then "Believe on the Lord Jesus Christ and thou shalt be saved," (Acts 16:31)