Answer:
The story Cain and Abel teaches us not to be jealous or there will be bad consequences in the future. Not only had Cain taken his brother life, he had also gotten himself banned by God and became an wander.
Also it could be that Abel offered the best of his what he produced. But Cain didn't. With jealousy, Cain killed Abel. And God punished him.
I hope this helps.
