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).