If thou doest well, will not [thy countenance] look up [with confidence]? and if thou doest not well, sin lieth at the door; and unto thee [shall be] his desire, and thou shalt rule over him.
God refused Cain's offering, and Cain was furious. God answers with a question, not a verdict, and two phrases in it are disputed: what "doing well" means, and whether what waits at the door is sin or a sin-offering.
God Speaks Before Cain Acts
The refusal of his gift had already turned Cain bitter, and God's response was not silence but speech aimed at that bitterness.
Cain, like every unbeliever, had no sense of the truth. He thought himself able to come to God with gifts of the earth, which expressed neither sin nor death, neither judgment nor expiation. How could Jehovah accept him or his offering? Nor was this all. God's acceptance of Abel drove his proud spirit into fury and lasting hatred. On the surface, its object was Abel, his righteous and weak brother. In reality, and beyond all, its object was God's grace. Jehovah stepped in with words of truth and grace, all in vain.
Why the Standard Never Moves
The offer "if you do well" rests on something in God that Cain's mood could not shift.
The principles of God's nature are unchanging. Whether people are believers or not, whether they receive the truth or not, God holds to what belongs to His own moral being... So with Cain here — "and if you do not do well;" and such was the fact. His condition was that of a sinner, and he did not look outside himself to God. Certainly he did not do well. Evil conduct is what makes an evil state plain, and it flows from that state.
What "Doing Well" Would Have Looked Like
Doing well meant owning what he was. Abel had already shown what that looks like.
But to do well was to own, as Abel did, what one born in sin needed. How little men understand this! Yet what higher or truer ground could Abel take than simply to confess what he was? It was in this that Cain had failed.
Sin — or a Sin-Offering?
Commentators differ on the second half of the verse. One Hebrew word carries both "sin" and "sin-offering," and the word for crouching pictures an animal lying down. Some writers argue that what crouches there is a victim, waiting to be offered.
"Sin" and "sin-offering" are the same word, whether in Greek or Hebrew. But what force would there be in "if you do not do well, sin crouches at the door"? That the last expression refers to an animal seems plain. Some interpreters take it as a picture, as if sin were a wild beast about to spring. Surely too late, when one has already sinned! Would it not rather be the provision of mercy for one who needs it — an offering not far to seek, but at the very door?
Others read the word as plain sin. They say no separate offering for sin was known this early.
I do not think the expression means a sin-offering, as some suppose. There seems to be no ground for saying that the truth of a sin-offering was understood in the slightest degree until long afterwards... Until the law came in, as far as Scripture tells us, there was no such distinction between the offerings. They were all merged in one.
Either Way, a Remedy Was Named
One writer weighed both readings and refused to press the point, because the two senses converge on the same mercy.
I would not want to speak too firmly about Genesis 4:7... Now I do not doubt that this speaks of Cain's guilt. The only question is whether it also presents that guilt in the way God has presented it to us — that is, in Christ as the sin-offering... I understand the primary sense to be, sin is there before you; you meet it as you go out; it lies at your door. He could not escape finding it attached to him: only God has laid it before us in the sin-offering in Christ.
His Place as Elder Brother Was Not Taken From Him
Abel's acceptance had not stripped Cain of anything, and the closing words of the verse say so.
There was no ground in any case for anger or despair. God is the God of grace now, as later He will judge by the Man He has raised from the dead... Meanwhile the unbeliever keeps the title of the firstborn over the younger brother who believes, just as the man keeps his place over the woman. What a just God is ours, even to an unjust Cain!
The Road He Would Not Take
Everything Abel had, Cain was invited to have on the same terms.
Cain had the same opportunity of securing acceptance and blessing as Abel, but he missed it. Mark that!... The Lord says in effect to Cain: You can go and do as Abel did. Follow your brother. Why don't you take his road? Sadly, Cain did not like it.
Summary
- Door — everything in the verse gathers at one place: what Cain needed was not far off but waiting at the very door.
- Grace — God met an angry man whose gift He had refused, and still spoke words of truth and grace.
- Confession — to "do well" was to own what one born in sin needs, the ground Abel took and Cain would not.
- Debate — writers differ on whether sin crouches at the door or a sin-offering does. Either way Cain is guilty, and either way God has set the remedy before us in Christ.
- Refusal — Cain kept his place as firstborn and the way of acceptance stood in front of him, but he would not take it.