The nature of Cain is part of our makeup as human beings.
What is a person’s purpose in this world?
To put it simply – as the text hints, “There was no man to till the soil” (Gen. 2:5) – his task is “to till it and tend it” (2:15).
Man is charged with preserving the world.
He is the one who must water the trees and ensure that nothing is damaged.
But surely man’s task cannot be summed up as being the Garden of Eden’s caretaker, to tighten loose screws and clean up spills here and there.
Man is charged with a greater mission, namely, “which God created to do (laasot).”
Man was created to take dynamic action, not just to preserve the present state of things.
–Rabbi Adin Steinsaltz