"And Cain said unto the Lord, My punishment is greater than I can bear (Gen. 4:13). Was it possible to talk like this before the countenance of God, Who is strict of course in righteousness, but is always ready to have mercy upon a sinner who truly repents? Envy obscured sensible thoughts, deliberate transgression hardened his heart, and behold, Cain rudely answers to God Himself: Am I my brother’s keeper? (Gen. 4:9). God wants to soften his stony heart with the hammer of His strict judgement; but Cain does not give in, and locked in his coarseness, he commits himself to the lot which he prepared for himself through his envy and murder. What is amazing is that after this he lived like anyone else: he had children, established a household and maintained earthly relations. Yet the mark of being outcast and of his despair still lay on him. So it is an inner affair, which occurs in the conscience, out of the realization of one’s relation to God, under the influence of burdensome passions, sinful habits, and deeds. Let people heed this now especially! But together with this let people resurrect their belief that there is no sin greater than God’s mercy; however, both time and work are needed to soften the heart. But it is either salvation, or ruin!"
- Saint Theophan the Recluse