Genesis 4:6

2 Later she gave birth to Cain’s brother Abel. Now Abel was a keeper of sheep, while Cain was a tiller of the soil.

3 So in the course of time, Cain brought some of the fruit of the soil as an offering to the LORD,

4 while Abel brought the best portions of the firstborn of his flock. And the LORD looked with favor on Abel and his offering,

5 but He had no regard for Cain and his offering. So Cain became very angry, and his countenance fell.

6 “Why are you angry,” said the LORD to Cain, “and why has your countenance fallen?

7 If you do what is right, will you not be accepted? But if you refuse to do what is right, sin is crouching at your door; it desires you, but you must master it.”

8 Then Cain said to his brother Abel, “Let us go out to the field.” And while they were in the field, Cain rose up against his brother Abel and killed him.

9 And the LORD said to Cain, “Where is your brother Abel?” “I do not know!” he answered. “Am I my brother’s keeper?”

10 “What have you done?” replied the LORD. “The voice of your brother’s blood cries out to Me from the ground.

Read all of Genesis 4