What does Genesis 4:12 mean?

In the previous verse, God began to pronounce His curse on Cain for murdering his brother Abel. Here, He concludes it. In addition to no longer being able to get crops from the ground, Cain would become a fugitive and a wanderer on the earth. He would be forced to separate from his family and seek other places to find food and shelter to survive.

Cain's curse is revealing. Even Cain, evil in his heart (1 John 3:12), found some satisfaction in working the ground to produce crops to feed himself and others. God took away what had brought some meaning and purpose to his life. In addition, of course, God drove Cain away from his family as He had driven Adam and Eve away from their home in the garden. Sin always leads to separation.

Interestingly, God does not yet demand Cain's life in response to his murderous act. God will later demand exactly that from His people, in response to the murder of the innocent. He does not kill Cain to satisfy justice for the murder of his brother, and He doesn't require Cain to make any animal sacrifice to atone for his sin. This seems to be extended as one last gesture of mercy. Cain, according to the following verses, will not only defy God's punishment by building a city (Genesis 4:17), he will produce a culture of evil, rebellious people.