"The Lord said unto Cain, Where is Abel thy brother? And he said: I know not: Am I my brother's keeper?"-- Gen_4:9.
"He that hateth his brother is in darkness, and walketh in darkness."-- 1Jo_2:11.
MAN'S FALL, whatever else it may have been, resulted in a complete change of the centre of his being. He was made in the likeness of God, and God's nature is absolutely selfless. God's will and purpose was the one rule of man's existence until the moment came when our first parents substituted the gratification of self for the will and law of God. From that hour the self-life became the dominant principle of mankind, and the world is what it is because the essence of life is the service of self.
We do not know what really caused the difference in the disposition of Cain and Abel. There are hints and suggestions, but the fundamental reason why these two brothers differed so is veiled in mystery, though the like of it still shows itself in our homes. St. John gives us the clue in his first Epistle, where he says that Cain slew his brother, because his own works were evil, and his brother's righteous.
God remonstrated with Cain and warned him that sin was lying at the door of his heart, waiting to enter. He exhorted him to watch and not allow it to intrude. When the dreadful deed was done, Cain found that all nature was in arms against him, and he became an outcast. The blood of Abel cried against Cain, for all sin cries to God, and He is the Avenger and Vindicator of wronged ones who in simplicity and faith have cast themselves upon Him. Thank God, also, there is a cry louder than that of Abel's, which pleads not for judgment but for mercy (Heb_12:24).
This world is full of envy, jealousy, strife, and murder, because men keep themselves instead of keeping their brothers; because our own instead of another's welfare revolves round the pivot of "I". The first Epistle of St. John is the antipode of this story in Genesis, and contains its corrective, for it is when we love God first and best that we love our brother, and as we open our whole soul to the tidal wave of God's love, we are lifted above the jagged rocks of the self-life into the broad full ocean of life which is life indeed (1Jo_3:14-17).