Genesis 4:5b Cain was very angry, and his face was downcast.
Cain thought his offering was perfectly fine, and that God was lucky to have it. He should have received God’s favor, he thought, not his frown. What kind of God would disapprove of an offering anyway? Cain wasn’t sure that he even liked God very much. Then the Lord said to Cain, Why are you angry? Why is your face downcast? If you do what is right, will you not be accepted? (Genesis 4:6-7).
God was not being unreasonable; he simply wanted Cain to understand worship. Cain’s offering showed a measure of compliance, but it wasn’t from his heart. Giving to God seemed like a tax to Cain, not an expression of love. So God assured Cain that he would be accepted if he simply did what was right.
Genesis 4:7b But if you do not do what is right, sin is crouching at your door; it desires to have you, but you must rule over it.
God used a powerful image to illustrate Cain’s struggle with sin—and ours. Sin is not a cuddly kitten, but a savage carnivore ready to devour. Cain could do the right thing, and be accepted by God, or he could do as he pleased, and be devoured by sin.
Many face a similar choice at one time or another. Some choose to conquer lust, others are devoured. Some choose to conquer drugs, others are devoured. Some choose to conquer hate, others are devoured. Sin is not a paper tiger, but a ferocious beast hungry for souls.