Mark 3:28-30
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28Most assuredly I tell you, all their sins will be forgiven to the sons of men, and their blasphemies with which they may blaspheme; 29but whoever may blaspheme against the Holy Spirit never has forgiveness, but is guilty of an eternal sin" 30-- because they said, "He has an unclean spirit."
Mark 3:28-30 (WEB)