What sin does God not forgive?

The Unforgivable Sin Explained

In Christian theology, discussions around forgiveness often lead to a specific and solemn concept found in the gospels: the eternal sin. According to the New Testament, Jesus addresses a unique spiritual boundary regarding what is traditionally known as the blasphemy against the Holy Spirit.

In the Gospel accounts—specifically in Mark 3:29 and Matthew 12:31–32—Jesus makes a clear distinction. He notes that many types of sins and blasphemies, even those spoken against the Son of Man, can ultimately be forgiven. However, speaking against or persistently rejecting the Holy Spirit stands apart as a permanent, eternal offense carrying no forgiveness.

Throughout history, theologians and scholars have interpreted this passage in various ways. Many view it not as a single accidental word or a momentary failing, but rather as a deliberate, hardened, and final state of the heart. In this view, a person commits this sin by willfully and permanently rejecting God's grace and attributing the clear, undeniable work of the Holy Spirit to evil, thereby cutting themselves off entirely from the source of repentance and forgiveness.