What does Genesis 4:8 mean?

In the previous verses, God accepted an offering from Abel, but rejected a different sacrifice from Cain. Scripture gives no explicit reasons why, but it seems to be a matter of Cain's attitude. Rather than attempting to do right, when corrected by God, Cain responds with anger. God warned Cain that his refusal to choose God's standards would cause him to lose the battle with sin. Cain, however, would not change course.

Despite God's loving, clear warning, Cain allows sin to win. Cain talked to his brother, and the two went to the field together. In some manuscripts, the text specifies that Cain wanted to go out into the field with Abel.

There Cain attacks and kills Abel: the first recorded murder in human history. Cain failed to live up to God's standards, and was angry. When God gave Cain a way to be restored, and warned him about the dangerous nature of sin, Cain instead chose to reject God even further. Cain would not be altered from his course of hurt, anger, and envy.

The Apostle John holds Cain out to us as a negative example, calling Cain "the evil one" (1 John 3:12), revealing that he was motivated by jealousy for his righteous brother.