Some worry they have committed an unpardonable sin. Jesus Christ's perfect sacrifice can cover any sin, so what could make a sin so bad God wouldn't forgive it.
Many have asked about what is often called the unpardonable sin.
Christ mentioned this unforgivable sin in Mark:3:28-29, where it is described as blasphemy against the Holy Spirit. It had to do with denying the authority and power of God. Mark explains that Christ was responding to an accusation from His detractors, who said, "He has an unclean spirit" (verse 30). They meant that His authority came from Satan, not from God. Although these accusers knew that Christ was the Son of God, they accused Him of being a fraud. Christ warned them that they were in danger of committing a sin for which there was no forgiveness.
What is the fate of one who does not repent of this sin? The unrepentant will die in a lake of fire at the end of the age (Matthew:10:28; Revelation:20:14-15). It's not that one sin is more terrible than another is, but rather that any sin we don't repent of will result in death. Hebrews:6:4-6 and Hebrews:10:26-27 both mention this sin as well, warning us not to "fall away" or to "sin willfully." How does one know if he has crossed the point of no return?
So long as one desires to repent, to get his or her life back in order spiritually, God will always forgive. Sadly, it is possible to come to a state of not caring about and not looking for forgiveness. If there's no repentance, there can be no forgiveness. That's when a person is in danger of the unforgivable sin. A person can come to that place either by simply drifting away or by sharply turning away from God in angry hostility.
At any time, God can and will forgive the sin of departing from Him, if the sinner wants forgiveness and genuinely repents. God inspired John to write, "If we confess our sins, He is faithful and just to forgive us our sins and to cleanse us from all unrighteousness" (1 John:1:9). Clearly, God will extend mercy to all who sincerely repent and change—regardless of their sin. Christ's words, coupled with the warnings in Hebrews, are sobering. Nonetheless, we should hold fast to the hope that God will grant us repentance when we turn to Him.
Let's broaden the subject to consider a related aspect. Quite apart from the unpardonable sin, many sincere religious people do not understand that sin is the transgression of God's law (1 John:3:4). Most churches teach and practice a theology much different from the way of life followed by the early New Testament Church of God.
For more understanding, please read our booklet The Road to Eternal Life .