Jesus talks about the unforgivable offence or sin in Mark 3:28-29. “Assuredly, I say to you, all sins will be forgiven the sons of men, and whatever blasphemies they may utter; but he who blasphemes against the Holy Spirit never has forgiveness, but is subject to eternal condemnation.”
The Holy Spirit testifies of Jesus. Testifying of who Jesus is and what He has done convicts those who do not receive and believe in Jesus’ flesh and blood sacrifice of Himself of all offences done against God and each other.
the unforgivable offence
A person may reject Jesus in ignorance and upon repentance receive forgiveness. However a person who knows the truth, yet attributes Jesus’ healing work to the works of evil, denies the conviction of the Holy Spirit. Consequently they deny their pathway to forgiveness committing the unforgivable offence.
As a result of this ongoing state of wilful rejection and false witness, a person cannot receive forgiveness. Due to their misrepresentation of the testimony of the Holy Spirit they are subject to eternal damnation. Jesus exposes their deception.
All who have received and believed in Jesus cannot commit such an offence. They have believed the testimony of the Holy Spirit and received Jesus’ sacrifice. In receiving Jesus they receive His free gift of salvation. Saved from punishment, judgement, payment and guilt of all offences done against God and against each other.
‘A cloud of darkness to those who rejected their Creator. His presence and light to those who received Him.’ @ineverystep