First of all, please notice in verse 12 God removed the gift that God alone had given Cain to be a farmer. Then we see he became both fugitive and vagabond. Both words indicate aimless wandering.
In the Hebrew fugitive is the word nûa‛ 5128 in Strong's and is a verb meaning to shake, to stagger, to wander. It refers to a displaced person, a wanderer, a vagrant. Vagabond is from the Hebrew word nûd 5110 in Strong's and is also a verb, but more emphatically has the sense of aimless motion or actions. It refers to a person moving about aimlessly without a home.
Brethren, all of mankind is on a journey, but the curse of sin to those not under the blood of Jesus Christ with eyes on Him and the goal of the Kingdom of God, is aimlessness in motion and in action on their journey.
How can good and bad be judged unless He instructed them? They knew what was good. They knew what was bad. Abel did what was good, but Cain, like his mother before him, shifted gears a little bit and substituted his own thinking regarding what would be acceptable to God. Verse 13 gives Cain's reaction. He was angry.
Again, God informed. Cain disobeyed. God judged. The pattern is followed. So it was Cain then, representing mankind, who was unjustly angry at God's judgment. In his eyes, he had become victimized by God. Thus we already see two patterns developing. First, God lets mankind know what He expects. His expectation is not even to the level of the New Covenant. At most it is the level of the Old Covenant. Secondly, mankind disobeys, and then feels unjustly treated in God's judgment.
Not only were Adam and Eve and their progeny separated from God and removed from dwelling with Him in the Garden of Eden, they were also separated from the source of life - the Tree of Life! The tragic results are very clear there for anyone to see! God simply and clearly expounds upon the result of sin. Next we have an example involving Cain and the curse coming upon him.
He is obviously concerned. There seems to be a measure of remorse in him, at least once he found out what the punishment was going to be - separation. We also find that God does not relent from what He wills to do.
