“Let’s go out into the field.” The phrase, “Let’s go out into the field” was dropped out of the Hebrew text by copyists, and does not appear in many versions. It has been properly restored in many modern versions from the Septuagint and Aramaic (cp. BBE; CEB; HCSB; NAB; NET; NIV; NJB; NLT; NRSV; RSV). There is a good chance that in his parable about the good and bad seed (Matt. 13:24-30, 36-43), Jesus took the illustration that “the field is the world” (Matt. 13:39) from the fact that Cain murdered Abel in the field.
“Cain rose up against Abel his brother and killed him.” Cain, the first son of Adam and Eve, was the first person to commit the unforgivable sin (Matt. 12:31-32) and become a child of the Devil. Cain became a child of the Devil by committing blasphemy against God in the time between Genesis 4:7 and 4:8. In Genesis 4:2-6, Cain had not given his best to God, and as a result, his sacrifice was not accepted. However, in Genesis 4:7, God told Cain that he could be accepted if he did “well,” i.e., did what God and wisdom directed. God also warned Cain that sin was close by, ready to pounce if it was given an opportunity. By portraying sin as a creature ready to pounce on Cain, God did His best to warn Cain, and us, of the Enemy that is always present and trying to turn us away from Him.
As late as Genesis 4:7, Cain could have repented and come back to God, but he did not. Instead of recognizing his sin and humbling himself to God, he arrogantly turned to the Devil as his god. After Genesis 4:7 God never again told Cain that there was a door of forgiveness and acceptance available to him. The New Testament lets us know that Cain became a child of the Devil: “Not as Cain, who was of that wicked one, and slew his brother. And wherefore slew he him? Because his own works were evil, and his brother’s righteous” (1 John 3:12 KJV). Thus, Cain was a child of the Devil when he murdered Abel, and murder is one of the things children of the Devil do to people who oppose them. The High Priest and his henchmen were children of the Devil and they wanted to murder Jesus Christ (John 8:37, 44).
Cain premeditated his murder of Abel, which is why he invited Abel into the field to get him away from the protection of the family (Gen. 4:8). Then, after murdering Abel, Cain lied to God about it and said he did not know where Abel was (Gen. 4:9), and lying is another one of the Devil’s primary traits, in fact, the word “Devil” means “slanderer,” and the Devil is the “father of lies” (John 8:44).
Cain was the first child of the Devil and the first person to commit what we now refer to as the “unforgivable sin.” Perhaps it was because he understood perfectly that he turned away from the true God and turned to the Devil to be his god that he knew that his sin could not be forgiven (Gen. 4:13).
[For more on the unforgivable sin, see commentary on Genesis 4:9, 10, 11, 13, 14, 15; and commentary on Matt. 12:31.]