Once there were two men who appeared before the Lord to present their sacrifices. One of them, the eldest, was a farmer, and his younger brother was a tender of herds. In order to appear before the Lord, it was necessary to present a sacrifice of blood, but the older brother was too proud to exchange anything with his brother. And so he presented his produce, and the Lord did not receive him. His younger brother made the appropriate sacrifice, and God was pleased with it.
The older brother was furious, and felt grievously wronged. But the Lord was kind to him and warned him about things he had no capacity to understand. Sin is crouching at the door, the Lord mysteriously said. And so the older brother waylaid his brother, and in the process was waylaid himself by the sin that God had warned him of.
The younger brother had the blood of animals on his hands, and so was innocent. The older brother refused to have such blood on his hands, and so he slid backwards (blind to himself) into the archetypical murder. He hands became bloody because he would not have bloody hands.
Our Lord said that the younger brother was righteous (Matt. 23:35). Our Lord’s apostle said that the older brother’s actions were evil (1 John 3:12). But this is not just an ancient story about an unfortunate incident at the beginning of the world. Abel is the father of many, and Cain is the father of the rest. The history of the world is a history of grasping, rivalry, and desire. But we go seriously astray if we think of this history of conflict as nothing more than dogs fighting over a piece of meat. Unrighteous men want what righteous men have, simply because they have it. But righteous men have it from the hand of God, and this is a blessing that, however envied, cannot be seized.
This means that you are either the older brother or the younger. The younger brother can give way to the elder brother in many ways, and is in fact called to it. But he cannot give way with regard to the required sacrifice—he is to sacrifice to the Lord, and not to his older and envious brother.
Abel, although he has no recorded descendents, is still the father of all who obey. Cain has many children, including those who crucified the Lord out of this family trait—treacherous envy. And so the history of the world is the history of this fratricide.