God gave the blessing of two sons to Adam and Eve–first Cain, then Abel.  Both brothers made an offering to the Lord, but the Lord only found Abel’s pleasing.  The text shows that God, in His wisdom and understanding of Cain’s heart, spoke to him, instructing Cain that his shortcoming in the offering didn’t have to turn into bitterness and revenge.  God empowered Cain to stand firm, humble and obedient, fleeing from Satan’s newest ploy to ensnare him (Cain) in the web of death.  God instructed Adam to rule over the animals of the Earth, and here God tells Cain to rule over the sinful impulses that desire to destroy him.

Unfortunately, Cain did not heed the Lord’s caution.  Instead of ruling over sin, he was ruled by violence and killed his brother, likely believing Satan’s second-oldest lie–that killing another person will better one’s own standing.

“And the Lord had regard for Abel and his offering, but for Cain and his offering he had no regard.  So Cain was very angry, and his face fell.  The Lord said to Cain, ‘Why are you angry, and why has your face fallen?’  If you do well, will you not be accepted?  And if you do not do well, sin is crouching at the door.  Its desire is for you, but you must rule over it.’ “Cain spoke to Abel his brother.  And when they were in the field, Cain rose up against his brother Abel and killed him.” – Genesis 4:4b-8