And Cain talked with Abel his brother: and it came to pass, when they were in the field, that Cain rose up against Abel his brother, and slew him.
All Commentaries on Genesis 4:8 Go To Genesis 4
Symeon the New Theologian
AD 1022
Why did Cain become a fratricide? Was it not by his evil will? He preferred himself to his Creator and followed after evil thoughts and so became abandoned to envy and committed murder.