What is the “unforgivable sin”?

Matthew 12:31“So I tell you, every sin and blasphemy can be forgiven—except blasphemy against the Holy Spirit, which will never be forgiven.”

Mark 3:28-29“I tell you the truth, all sin and blasphemy can be forgiven, but anyone who blasphemes the Holy Spirit will never be forgiven. This is a sin with eternal consequences.”

Blasphemy against the Holy Spirit is called an “unforgivable sin.” The reason it is unforgiveable is because it reflects a settled, hardhearted attitude of defiant hostility toward God. A person who has that attitude will never come to God for forgiveness, so such a sin is unforgivable. Anyone who is worried about whether he or she has committed the unforgivable sin, proves that he or she has not.