Adam and Eve must have taught their sons how to worship God with a sacrifice. They had learned it themselves from the example of how God covered their sins back in Eden (Genesis 3:21), when God took the life of an innocent animal, shedding its blood, to cover their newly-acknowledged nakedness with “skins.”
Abel followed that example, shedding the blood of an innocent animal and presenting it to God as a sacrifice for the guilty sinner (foreshadowing the death of Christ, the ultimate sacrifice for sin).
But Cain did not. His self-styled offering of fruits and vegetables was a useless, bloodless, faithless sacrifice. Hebrews 11:4 and 1 John 3:12 make it clear that Cain’s failed attempt at worship was not made in ignorance or naïveté.
Verse 7 is the key verse in this chapter. It tells of the grace of God in offering Cain a second chance to “do well” and “be accepted.” God’s grace is about do-overs and beginning again.
This verse also speaks to the danger of not responding to God’s grace and turning from sin. God said that sin was “crouching at the door,” ready to waylay Cain if he did not repent. Think about that warning. Sin will control you if you let it. But God told Cain that he could “rule over” sin. Cain didn’t have to give in…he could conquer sin…and I can, too.
So I have a choice today: I can live for God’s glory. I can live by God’s guidelines. I can respond to God’s grace and deal with my sin His way. If I do that, I will enjoy His presence and His fellowship.
Or like Cain, I can try to deal with sin my way, refusing to admit that I’m wrong, and destroying others to make myself look better. If I do that, I will find myself separated from the presence of the Lord (v.16) and settling for an aimless, wandering life (“Nod” means wandering).