Questions 150 to 151
This section looks at why priests have the authority to forgive sin, and at the different ways in which our sins are forgiven.
See Your Sins are Forgiven.
The sin against the Holy Ghost which Christ warned us would not be forgiven in heaven or on earth is persistent impenitence, the sin of one who rejects conversion and dies in mortal sin. One guilty of this sin can never obtain forgiveness of God, because at the hour of death he continues to thrust God away from him.