What is blasphemy against the Holy Spirit? Though many suggestions have been offered, I think the answer lies in the context here (Mark 3:29-29) and in the context of redemptive history. Remember that the Holy Spirit had not yet been poured out, and it is the Spirit who causes men to recognize who Jesus is. Hebrews 6 and 10 contain discussions of unforgivable sins, but the distinction between blasphemy against Christ and the Spirit has disappeared. Jesus seemed to be saying this: Because the Holy Spirit has not yet been poured out in fullness, the Jews will be forgiven for blaspheming the Son of Man. They will be given a second chance to repent, as we see in the book of Acts. If, however, they continue to blaspheme after the Spirit has come, they will not be forgiven. But what is the sin, specifically? Since it is blasphemy, we must see it essentially as a verbal sin. In context, it is the sin of saying that Jesus Christ is of the devil. Jesus was willing to excuse this blasphemy before Pentecost; but, in the new covenant era it is not longer excusable. If a person curses Jesus, but does not really know who Jesus is, that sin is forgivable. However, if the Holy Spirit has borne witness to a person that Jesus is indeed the Son of God, and that person curses Him, it cannot be forgiven.  Tabletalk, July 12, 1990.