Blasphemy Against the Holy Spirit
From Anstey’s Doctrinal Definitions:
Blasphemy is speaking derogatorily of the Persons of the Godhead. This is what the faithless “generation” of Jews (Matt. 12:39, 42) did when they saw the Lord. “Blasphemy against the Holy Ghost” is the national sin of the Jews who lived at the time when the Lord came (Matt. 12:24-32). Mark 3:29-30 tells us specifically what this sin is. It says, “Because they said, He hath an unclean spirit.” Thus, they attributed the power that worked in the ministry of the Lord Jesus to Satan (Matt. 12:24; Mark 3:22; Luke 11:15). They said that the Lord Jesus was associated with, and empowered by, Satan’s underworld in His ministry, which is preposterous! This blasphemy against the Holy Spirit brought an unpardonable judgment of “eternal damnation” on the unbelieving portion of the nation (Psa. 69:22-28).
Sad to say, there are people today who think that they have committed this sin and by doing so, they have damned themselves, and now there is no hope for them of being saved. They call it, “The Unpardonable Sin.” However, this is a lie of the devil. The Bible does not teach that blasphemy against the Holy Ghost is something that an individual commits, but rather is the national sin of Israel. In view of what Scripture says that “blasphemy against the Holy Ghost” is (Mark 3:30), let those who think they have committed the so-called "unpardonable sin" ask themselves, “Is the Lord Jesus Christ truly the Son of God who came from heaven to save sinners?” If their answer is, “Yes,” then that is a clear proof that they haven’t committed the unpardonable sin of blasphemy against the Holy Spirit! What Christian would ever say that the Lord Jesus had “an unclean spirit?” No backsliding Christian harbours the thought that the Lord Jesus came from the underworld to do Satan’s work. It is only something that an apostate person would say. (See Apostasy.) However far away from the Lord a Christian backslider may get in his soul, there is still, somewhere in the deep recesses of his heart, the sincere conviction that the Lord Jesus Christ came from heaven as the Saviour of sinners.
Even if someone today has said derogatory things about the Person of the Lord Jesus Christ, he or she can still be saved, for Scripture says, “The blood of Jesus Christ His Son cleanseth us from every sin” (1 John 1:7). C. H. Mackintosh said, “We do not believe that any sinner, in this acceptable year, this day of salvation (Luke 4:17-19), is beyond the reach of the pardoning love of God, and the atoning blood of Jesus.” Paul the Apostle was a “blasphemer” and God saved him! (1 Tim. 1:13)