Genesis 4:2

4:2 Then she gave birth to his brother Abel. Abel took care of the flocks, while Cain cultivated the ground.

Genesis 4:4

4:4 But Abel brought some of the firstborn of his flock – even the fattest of them. And the Lord was pleased with Abel and his offering,

Genesis 4:8

4:8 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.