What is the Unforgivable Sin?

In Mark 3:28-29, Jesus delivers a sobering warning:

²⁸“Truly I say to you, all sins shall be forgiven the sons of men, and whatever blasphemies they utter; ²⁹but whoever blasphemes against the Holy Spirit never has forgiveness, but is guilty of an eternal sin”

This statement arises from an encounter with religious leaders who accused Jesus of casting out demons by the power of Satan (Mark 3:22). In essence, they were attributing the clearly divine work of the Holy Spirit to the devil.

Blasphemy against the Holy Spirit is not a careless word or momentary doubt. It is a willful, informed, and continuous rejection of the Spirit's testimony that Jesus is the Son of God. This sin is unforgivable not because God withholds grace, but because the person refuses the very means by which forgiveness is granted–repentance prompted by the Holy Spirit.

In practical terms, this sin is committed by someone who has seen the evidence of God's power, recognizes it for what it is, and still calls it evil. It is a hardened spiritual posture that will not–and eventually cannot–repent.

This warning does not apply to believers who struggle, stumble, or even deny Christ in weakness (as Peter once did). Nor is it about speaking a single blasphemous word. Rather, it is about an entrenched resistance to God's truth, an outright rejection of the Holy Spirit's work in pointing to Jesus.

The very fear of having committed this sin is often a clear sign that one has not. A heart that still feels conviction is a heart still open to God. Jesus' warning is not meant to discourage the humble, but to expose the danger of a proud and unrepentant heart that refuses the Spirit's witness.