(article from equip.org)
How can I be certain that I’ve not committed the unforgivable sin?
This is one of the most frequently asked questions on the Bible Answer Man broadcast and stems from the following words spoken by Christ: “I tell you the truth, every sin and blasphemy will be forgiven men, but the blasphemy against the Spirit will not be forgiven. Anyone who speaks a word against the Son of Man will be forgiven, but anyone who speaks against the Holy Spirit will not be forgiven, either in this age or in the age to come” (Matthew 12:31–32). As a result of these words, Christians are often paralyzed by fear.
In response, let me first point out that from a historic perspective the Pharisees mentioned by Matthew militantly hated Christ and attributed his miracles to Beelzebub, the prince of demons. Unlike those who are afraid they have committed the unforgivable sin, the Pharisees were totally unconcerned about Christ’s forgiveness. Instead, with premeditation and persistence, they willfully blasphemed the Holy Spirit’s testimony that Christ was the Son of the living God. It is crucial to recognize that the unforgivable sin is not a single act but a continuous, ongoing rejection.
Furthermore, those who have committed the unpardonable sin have no godly regrets. As Paul emphasizes in the book of Romans, they not only continue in their evil ways but approve of others who do so as well (Romans 1:32). Conversely, “godly sorrow brings repentance that leads to salvation” (2 Corinthians 7:10). Sorrow for sin and the desire for Christ’s forgiveness is proof positive that you have not rejected the Savior of your soul. Never forget that three times Peter denied his Lord with vile oaths. Yet, not only did Christ forgive him, but his confession, “You are the Christ, the Son of the living God” (Matthew 16:16) became the cornerstone of the Christian church.
Finally, the Bible consistently teaches that those who spend eternity separated from God do so because they willingly, knowingly, and continuously reject the gospel. John refers to this as the “sin that leads to death” (1 John 5:16) in the sense that those who refuse forgiveness through Christ will spend eternity separated from his grace and love. Be assured that those who sincerely desire God’s forgiveness can be absolutely certain that they will never be turned away.
“I write these things to you who believe in the name of the Son of God so that you may know that you have eternal life.” 1 John 5:13