Genesis 4:2-5

Then she bore again, this time his brother Abel. Now Abel was a keeper of sheep, but Cain was a tiller of the ground. And in the process of time it came to pass that Cain brought an offering of the fruit of the ground to the LORD. Abel also brought of the firstborn of his flock and of their fat. And the LORD respected Abel and his offering, but He did not respect Cain and his offering. And Cain was very angry, and his countenance fell.