Genesis 4:6-8

New Catholic Bible

⁶ The Lord therefore said to Cain, “Why are you angry and why has your countenance fallen? ⁷ If you do what is right, will you not be able to hold up your head? But if you do what is wrong, sin is crouching at your door. It seeks to dominate you, but you can overcome it.”

⁸ Cain said to his brother Abel, “Let us go out into the fields.” While they were walking in the fields, Cain attacked his brother Abel and killed him.