The taking no notice of sin keeps iniquity in good spirits, belittles the sanctity of law and blurs the conscience.
With God also penalties are warnings.

His punishments are thorn hedges, safeguarding man from the thorns and thickets where serpents brood, and forcing his feet back into the ways of wisdom and peace.
For man's integrity and happiness, therefore, conscience smites and is smiting unceasingly.

Therefore, Eugene Aram dared not trust himself out under the stars at night, for these stars were eyes that blazed and blazed and would not relent.

But why did not the murderer, Eugene Aram, forgive himself?
When Lady Macbeth found that the water in the basin would not wash off the red spots, but would "the multitudinous seas incarnadine," why did not Macbeth and his wife forgive each other?
Strange, passing strange, that Shakespeare thought volcanic fires within and forked lightning without were but the symbols of the storm that breaks upon the eternal orb of each man's soul.

If David cannot forgive himself, if Peter cannot forgive Judas, who can forgive sins?
"Perhaps the gods may," said Plato to Socrates.