Genesis 4:6-8 New Revised Standard Version Catholic Edition (NRSVCE)
6 The Lord said to Cain, “Why are you angry, and why has your countenance fallen? 7 If you do well, will you not be accepted? And if you do not do well, sin is lurking at the door; its desire is for you, but you must master it.”
8 Cain said to his brother Abel, “Let us go out to the field.”[a] And when they were in the field, Cain rose up against his brother Abel, and killed him.