Genesis 4:3-7 (New International Version)

³ In the course of time Cain brought some of the fruits of the soil as an offering to the LORD. ⁴ But Abel brought fat portions from some of the firstborn of his flock. The LORD looked with favor on Abel and his offering, ⁵ but on Cain and his offering he did not look with favor. So Cain was very angry, and his face was downcast.

 ⁶ Then the LORD said to Cain, "Why are you angry? Why is your face downcast? ⁷ If you do what is right, will you not be accepted? But if you do not do what is right, sin is crouching at your door; it desires to have you, but you must master it."