“Behold.” Of Cain’s four statements in Genesis 4:14, the first three are true. First, he was indeed driven from the “face” of the ground. The word “face” represents intimacy, a closeness of relationship. Scripture had told us earlier that the soil would not produce well for him. Second, Cain was hidden from the “face” of God, i.e., from an intimate relationship with Him. Many of the Devil’s people have a lot of “head knowledge” about God, but they do not really know Him and they cannot be intimate with Him. This explains why there are religious leaders in Christ’s time as well as through the ages who seem to have theological knowledge but whose hearts are far from God. Third, Cain became a vagrant on the earth, someone who could not make a home on it and live a satisfied life.
Given the truth of the first three sentences, there is every reason to believe that Cain’s fourth statement, that he would be killed, would have also proven true if God had not intervened. But God did intervene, and Cain was able to go on living. Cain said, “whoever” found him would kill him. In these early generations after the Fall, mankind was not specifically commanded to police each other, as they were after the Flood, starting with Genesis 9:6. Nevertheless, people recognized good behavior and evil behavior, just as they do now. The sin of becoming a child of the Devil and having to prey on other people was so heinous that it would elicit a kind of vigilante action, by which good people would kill Cain due to the evil actions that would flow out of his evil nature. God intervened so that Cain and people like him would have a choice between good and evil, between God and the Devil, not that there is no justice for evil acts, but people are not executed simply for following the Devil (see commentary on Gen. 4:15).
“face.” The Hebrew is literally, “face,” and it means “surface.” Cain’s relationship with the ground has now changed. Cain was a worker of the soil, the ground, but now he has become evil and God will not bless the ground for him. Cain will no longer be able to farm as profitably as before. So Cain built a city so he could take advantage of the work of others.
“and whoever finds me will kill me.” The only “whoever” on the earth are the descendants of Adam and Eve, so it seems like Cain is saying that because he murdered Abel, any descendants of Adam and Eve would have the right to kill him as a matter of justice and blood vengeance.