Jesus explains that blasphemy against the Holy Ghost will not be forgiven.
26 Verily, verily, I say unto you, if a man marry a wife according to my word, and they are sealed by the aHoly Spirit of promise, according to mine appointment, and he or she shall commit any sin or transgression of the new and everlasting covenant whatever, and all manner of blasphemies, and if they bcommit no murder wherein they shed innocent blood, yet they shall come forth in the first resurrection, and enter into their exaltation; but they shall be destroyed in the flesh, and shall be cdelivered unto the buffetings of dSatan unto the day of eredemption, saith the Lord God.
23 And blasphemies, wherewith soever they shall blaspheme, shall be forgiven them that come unto me, and do the works which they see me do.
65 Then the high priest rent his clothes, saying, He hath spoken ablasphemy; what further need have we of witnesses? behold, now ye have heard his blasphemy.
12 And thou shalt know that I am the Lord, and that I have heard all thy ablasphemies which thou hast spoken against the mountains of Israel, saying, They are laid desolate, they are given us to consume.
3 So he carried me away in the spirit into the wilderness: and I saw a woman sit upon a scarlet coloured beast, full of anames of blasphemy, having seven heads and ten horns.