In Matthew 12:31-32 the Pharisees had blasphemed against the Spirit by attributing the power by which Christ did miracles to Satan (12:24) instead of the Holy Spirit.  The unpardonable sin is the deliberate refusal to acknowledge God’s power in Christ.  It indicates a deliberate and irreversible hardness of heart.  Sometime believers worry that they accidentally committed this unforgivable sin.  But only those who have turned their backs on God and rejected all faith have any need to worry.  Jesus said they can’t be forgiven--not because their sin is worse than any other, but because they never ask for forgiveness.  Whoever rejects the prompting of the Holy Spirit removes themselves from the only force that can lead him or her to repentance and restoration to God.  Thus, a genuine believer in Christ could never commit this sin.  In Matthew 25:31-46; God will separate his obedient followers from pretenders and unbelievers.  The Bible further states in Romans 10:13; whoever calls on the name of the Lord shall be saved.