Genesis 4:2-5 NIV
Later she gave birth to his brother Abel.
Now Abel kept flocks, and Cain worked the soil. In the course of time Cain brought some of the fruits of the soil as an offering to the LORD. And Abel also brought an offering—fat portions from some of the firstborn of his flock. The LORD looked with favor on Abel and his offering, but on Cain and his offering he did not look with favor. So Cain was very angry, and his face was downcast.
NIV: New International Version