6 Then the LORD said to Cain, Why are you angry, and why is your expression downcast? 7 Is it not true that if you do what is right, you will be fine? But if you do not do what is right, sin is crouching at the door. It desires to dominate you, but you must subdue it.
8 Cain said to his brother Abel, Lets go out to the field. While they were in the field, Cain attacked his brother Abel and killed him.
A dark heart and a dark act
Any military veteran can tell you that it is never good to underestimate your enemy. Making matters worse, enemies do not always identify themselves as such. Sin is such an enemy, preferring to lie in wait for us or to deceive us into disobeying God.
How can emotions cloud our view of danger? How does information from God help us recognize the threats of sin? What resources do we have to defeat sin?
It is striking to see that God talks to Cain (Gen. 3:6), but Cain makes no reply! Not even Jonah in his fury practiced such stony silence (Jonah 4). Indeed, no other biblical example of such silence comes to mind. Alan Ross credits Derek Kidner with the observation that Cain would not be talked out of his intended sin, even by the Lord himself.
Genesis 4:7 Is it not true that if you do what is right, you will be fine? But if you do not do what is right, sin is crouching at the door. It desires to dominate you, but you must subdue it.
Many experts call Genesis 4:7 the most obscure verse in Genesis, though that is not apparent to the reader of the English Bible. Most of the difficulty occurs in Genesis 4:7a, which will be demonstrated below in the diversity of translations:
ESV: If you do well, will you not be accepted? (also NIV and RSV)
NASB: If you do well, will not your countenance be lifted up? (NASB uses italics for words supplied to complete the meaning.)
Hamilton: Look, isnt there acceptance if you do well . . . ?
Wenham: Is there not forgiveness if you do well?
The ideas of being accepted or forgiven or having ones countenance lifted up are all part of the possible meaning of the original verb. NET tries to split the difference by saying you will be fine, which sounds contemporary and takes no explicit position. Not only is this verb flexible, but the sentence ends abruptly, a phenomenon similar to Gods remarks in Genesis 3:22 which also end abruptly. In both cases the abrupt ending is immediately followed by dramatic action; in Genesis 3:23, God swiftly and forcefully expelled the man and woman from the garden; in Genesis 4:8, Cain suddenly murders his brother.
Not only does God offer Cain acceptance and forgiveness, he also gives a clear statement of danger and a challenge to overcome it (Gen. 4:7b). Personified sin faces Cain as surely as it had confronted Eve in the garden. Though sin first occurred in Genesis 3, the first explicit mention of the word occurs in Genesis 4:7.
The personification of sin in Genesis 4:7 should be a somber warning to all of us. Remember that the serpent in Genesis 3 was personified evil, not merely a member of Gods creation. When NET says sin is crouching, the standard lexicon says the verb means: literally sin is a lurker, meaning sin lurks.  A dictionary meaning for lurk is lie in wait, lie in ambush. God warns Cain that sin is waiting to ambush him! Sin is personal evil, and it does not fight openly.
God also tells Cain what he must do about this lurking danger: It desires to dominate you, but you must subdue it (Gen. 4:7b). Victor Hamilton says:
The word for urge [NET, desires] here . . . is the same word used in the previous chapter for Eves feelings toward Adam (3:16). Similarly, what Cain can do to sin —you are the one to master . . . it —is described with the same verb used for Adams actions with Eve (he shall be master over you, 3:16).
You can see that these chapters contain a constant and complex interplay of literary elements.
Genesis 4:8 contains another of those mysteriously abrupt sentences, which Hamilton explains:
It has long been observed that this verse omits what Cain actually said to his brother. The [Hebrew] text simply reads And Cain said unto Abel his brother. When they were in the field . . . On the basis of the ancient versions most modern translations insert something like: And Cain said unto Abel his brother, Let us go out to the field.
Two excellent English translations of Genesis 4:8 show the difference, as follows:
NET: Cain said to his brother Abel, Lets go out to the field. While they were in the field, Cain attacked his brother Abel and killed him.
ESV: Cain spoke to Abel his brother. And when they were in the field, Cain rose up against his brother Abel and killed him.
As you see, NET adds the words Lets go out to the field on the basis of several ancient translations of the Old Testament. The ESV sticks with the shorter version given by the Hebrew text. This writer joins Wenham and Hamilton in thinking the ESV translation is preferable. Cain rose up (ESV) fits with the ambush theme of Gods warning. The truncated sentence fits the pattern of the previous examples (3:22 and 4:7): sudden action follows immediately.
Cain thinks he has ambushed his brother, but sin has ambushed Cain! From that fateful day to this, the killing has never stopped. Sin lurks to ambush you at this very moment!
Copyright 2011 by Barry Applewhite, Plano, Texas. All rights reserved worldwide. Derived from material created for Christ Fellowship, McKinney, Texas. Used by permission.
 Alan P. Ross, Creation and Blessing (Grand Rapids: Baker Books, 1988) 158.
 L. Koehler, W. Baumgartner and J. J. Stamm, The Hebrew and Aramaic Lexicon of the Old Testament (HALOT), translated and edited under the supervision of M. E. J. Richardson. 5 vols. (Leiden, The Netherlands: Brill, 1994-2000) rabats, lurk, q.v.
 lurk. WordNet 3.0.Princeton University. 23 Sep. 2008..
 Victor P. Hamilton, The Book of Genesis: Chapters 1-17, The New International Commentary on the Old Testament (Grand Rapids: William B. Eerdmans Publishing Company, 1990) 227.
 Hamilton, Genesis 1-17, 229.