Many Christians wrestle with the question of whether they have blasphemed against the Holy Spirit. It is understood to be the unpardonable sin (see Matthew 12:32; Mark 3:29; Luke 12:10; Hebrews 6:4–5; Hebrews 10:26). The author proceeds to look at what has been said about this sin in past times and also in the present.
What is the unpardonable sin? This article explains.