God rejected Cain's offering. And when Cain was warned of the dangers of sin, he grew angry and his countenance fell. Once God had finished speaking to Cain,
Cain told Abel his brother... (Genesis 4:8)What exactly Cain told Abel is not specified in the text. However, it can be inferred that Cain told Abel of his encounter with God— that God did not have regard for his offering.
After Cain finished telling his brother, he waited for the right moment. He had already planned what he was going to do. Why should he allow his brother to continue in prosperity?
...And it came about when they were in the field, that Cain rose up against Abel his brother and killed him (Genesis 4:8).Cain murdered Abel. The deed was complete. For the first time in human history, one man murdered another man. This is anger carried out to its full extent. This is pure and total evil. Not only did Cain murder a man, but he, like Satan, wished to rule instead of God. Cain ultimately wished to take God off His throne— to murder God.
For this is the message which you have heard from the beginning, that we should love one another; not as Cain, who was of the evil one and slew his brother And for what reason did he slay him? Because his deeds were evil, and his brother's were righteous (1 John 3:11-12).Cain's actions were so vile that the apostle John portrays the opposite of love to be the same as a person who behaves like Cain.
It is important to point out that the story of Cain and Abel was a real event, not merely a symbol. Cain and Abel were real human beings who once walked on planet earth. In the New Testament, Jesus affirms the historicity of the story of Cain and Abel (Matthew 23:35, Luke 11:51). The story, however, of Cain (and not Abel) is far from over. Although the righteous Abel was slain, his brother continued to live out a rebellious life.
Cain and Abel: Sarcastic Reply - Genesis 4:9
Cain and Abel: Anger - Genesis 4:5-7
Psalm 1:1 - Traverse Not With Wickedness
Why Is Sin Unavoidable? (Part 1) - The Christian Worldview
How Bad Is Sin? (Part 1) - The Christian Worldview