Though the story of Cain and Abel begins with the hope Cain may be the one to bring humanity back to Eden (Gen. 4:1), it soon becomes evident all is not well with Adam’s firstborn. Having had his offering rejected by God (vv. 3–5a), Cain does not turn from his wickedness and reform his half-hearted, faithless worship. Instead he hardens his heart, angrily ruminating over his situation (v. 5b).
In today’s passage, the Lord warns Cain about the coldness of his spirit. “Why are you angry?” God inquires, not because He cannot see the man’s heart, but in order that Cain might know the Lord’s displeasure is due to his own sin. Just as with Adam (3:9), God mercifully gives Cain an opportunity to examine himself and repent.
This interpretation gains further support from verse 7. The ESV translates 7a as “If you do well, will you not be accepted?” “Accepted” can also be rendered “forgiven” for the sake of clarity. Basically, the Lord is telling Cain to soften his heart, turn from his unfounded anger, and begin to offer true worship. The context thus demonstrates that “do well” does not imply justification by works but that forgiveness comes only to those who repent.
The remainder of verse 7 is a sober warning to Cain of his need to heed the Lord’s warnings. God counsels Adam’s eldest son to beware of the sin “crouching” at the door lest he be unable to master it. There is a connection to the seed of the serpent here as the word “crouching” in other ancient Near Eastern literature is used of demons. Satan is seeking to use sin to dominate Cain, and he will be successful if Adam’s son does not turn from his unrighteous anger.
Cain’s rage is itself evil, but soon it will erupt into fratricide, a more heinous transgression. Though Cain is an unbeliever, the New Testament uses him as a warning for the faithful (1 John 3:11–15). By the Holy Spirit, all believers are enabled to live unto holiness (Rom. 8). However, we are foolish if we suppose that we are incapable of serious sin. An evil desire is the first step towards a more wicked act (James 1:14–15), and if we do not flee from evil desires, we may find ourselves ceding control to the serpent.
David’s wicked affair with Bathsheba and involvement in the death of Uriah (2 Sam. 11) began with an “innocent” glance at the woman’s beauty (v. 2). If we are not careful with what we look at, listen to, or think about, we may also join the list of believers who introduced tragedy into their lives due to the temporary reign of sin. If you struggle with a persistent sin, turn it over to God today, lest it master you. If necessary, seek accountability and counseling to overcome it.