Question: "What is the unpardonable sin / unforgivable sin?"
Answer: The unpardonable/unforgivable sin or “blasphemy of the Holy Spirit” is mentioned in Mark 3:22–30 and Matthew 12:22–32. Jesus said, “Truly I tell you, people can be forgiven all their sins and every slander they utter” (Mark 3:28), but then He gives one exception: “Whoever blasphemes against the Holy Spirit will never be forgiven; they are guilty of an eternal sin” (verse 29).
According to Jesus, the unpardonable or unforgivable sin is unique. It is the one iniquity that will never be forgiven (“never” is the meaning of “either in this age or in the age to come” in Matthew 12:32). The unforgivable sin is blasphemy (“defiant irreverence”) of the Holy Spirit in the context of the Spirit’s work in the world through Christ. In other words, the particular case of blasphemy seen in Matthew 12 and Mark 3 is unique. The guilty party, a group of Pharisees, had witnessed irrefutable evidence that Jesus was working miracles in the power of the Holy Spirit, yet they claimed that He was possessed by the prince of demons, Beelzebul (Matthew 12:24; Mark 3:30).
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