Genesis 4:5-8

5but on Cain and his offering he did not look with favor. So Cain was very angry, and his face was downcast. 6Then the Lord said to Cain, “Why are you angry? Why is your face downcast? 7If you do what is right, will you not be accepted? But if you do not do what is right, sin is crouching at your door; it desires to have you, but you must rule over it.” 8Now Cain said to his brother Abel, “Let’s go out to the field.” While they were in the field, Cain attacked his brother Abel and killed him.