Genesis 4:1-8

Adam slept with his wife Eve and she became pregnant. She gave birth to Cain, and said, “With the Lord's help I have made a man.” Later she gave birth to his brother Abel. Abel became a shepherd, while Cain was a crop farmer. Sometime later Cain brought some of the produce he'd grown as an offering to the Lord. Abel also brought an offering: the firstborn lambs of his flock, selecting the very best parts to offer. The Lord was pleased with Abel and his offering, but he wasn't pleased with Cain and his offering, which made Cain very angry and he frowned in annoyance. The Lord said to Cain, “Why are you so angry? Why do you look so annoyed? If you were doing what's right, then you'd be looking happy. But if you don't do what's right, then sin will be like an animal crouching outside your home, ready to pounce on you. It wants to have you, but you must be the one in control.” Later, when Cain was talking with his brother Abel they went out into the fields where Cain attacked his brother and killed him.