Here's what Martin Luther had to say about Cain and Abel...
This is an outstanding passage. Therefore it must be carefully taken note of and methodically studied. It would be sufficient if the New Testament had a statement praising the trust in God’s mercy over against the trust in works as clearly as it is praised here at the beginning of the world. When Moses says: “The Lord had regard for Abel and for his offering,” does he not clearly indicate that God is wont to look at the individual rather than at the work, to see what sort of individual he is? If, then, the individual is good, his work also pleases Him; but if the individual is not good, his work displeases Him. This observation that God has regard for the individual and only accepts works from those he considers righteous is key to understanding the text. Luther continues:
This is the essence of our teaching. We teach and confess that a person rather than his work is accepted by God and that a person does not become righteous as a result of a righteous work, but that a work becomes righteous and good as a result of a righteous and good person, just as the text here proves. Because God has regard for Abel, He has regard also for his offering; and because He has no regard for Cain, He has no regard for his offering either. The text gives clear support to this conclusion, and this cannot be denied by our opponents. Moreover, there follows from these words the very clear and very valid conclusion that Abel, rather than his work, was righteous and that the work pleases because of the person, not the person because of his work. The latter is what our adversaries maintain when they teach that a man is justified through his works and not by faith alone.
Thus the author of the Epistle to the Hebrews has looked at this passage with pure and clear eyes when he says (Heb. 11:4): “By faith Abel offered a more excellent sacrifice than Cain, by which he obtained witness that he was righteous, God bearing witness concerning his gifts.” Cain also brings an offering, and indeed first; but when he brings his offering, he is puffed up by the glory which was his by birth, and he hopes that the sacrifice will please God because it is brought by the first-born. Thus he comes without faith, without any confession of sin, without any supplication for grace, without trust in God’s mercy, without any prayer for the forgiveness of his sins. He comes in the hope that he will please God by nothing else than that he is the first-born. All the work-righteous do the same thing even now. They are concerned only with their own work, and so they hope that they will please God because of it; they do not trust in God’s mercy, and they do not hope that God will pardon their sins because of Christ. Cain, too, was such a person, for he could not have displeased God if he had had faith.
Abel, on the other hand, acknowledges that he is an unworthy and poor sinner. Therefore he takes refuge in God’s mercy and believes that God is gracious and willing to show compassion. And so God, who looks at the heart, judges between the two brothers who are bringing their offerings at the same time. He rejects Cain, not because his sacrifice was inferior (for if he had brought the shell of a nut in faith as a sacrifice, it would have been pleasing to God), but because his person was evil, without faith, and full of pride and conceit. By contrast, He has regard for Abel’s sacrifice because He is pleased with the person. Accordingly, the text distinctly adds that first He had regard for Abel and then for his sacrifice. For when a person pleases, the things he does also please, while, on the contrary, all things are displeasing if you dislike the person who does them.
Therefore this passage is an outstanding and clear proof that God does not have regard for either the size or the quantity or even for the value of the work, but simply for the faith of the individual. Similarly, by contrast, God does not despise the smallness, the lack of value, or the lowly nature of a work, but only a person’s lack of faith.
-- Luther’s Works, Vol. 1: Lectures On Genesis: Chapters 1-5 (ed. Jaroslav Jan Pelikan et al.; Saint Louis: Concordia Publishing House, 1999), Genesis 4:5
It's indeed true what Luther says about how "a person does not become righteous as a result of a righteous work, but that a work becomes righteous and good as a result of a righteous and good person," and the only way we are ever deemed a "righteous and good person" is by imputed righteousness received through faith in Jesus Christ's atoning sacrifice upon the cross for the sins of all mankind.
In a Lutheran layman's terms, and as Luther aptly pointed out, "God does not have regard for either the size or the quantity or even for the value of the work, but simply for the faith of the individual."
NOTE: Please understand that I'm not a called and ordained minister of God's Word and Sacraments. I'm a layman or just a regular Christian, Corporate Recruiter, Husband, Father, Friend who lives in the "City of Good Neighbors" here on the East Coast. As another Christian Blogger once wrote, "Please do not see this blog as me attempting to 'publicly teach' the faith, but view it as an informal Public Journal of sorts about my own experiences and journey, and if any of my notes here help you in any way at all, then I say, 'Praise the Lord!' but please do double check them against the Word of God and with your own Pastor." To be more specific, and relevant to the point I want to make with this disclaimer/note, please understand that I'm a relatively new convert to Confessional Lutheran who recently escaped American Evangelicalism a little more than 3 years ago now. That being said, please contact me ASAP if you believe that any of my "old beliefs" seem to have crept their way into any of the material you see published here, and especially if any of the content is inconsistent with our Confessions and Lutheran doctrine (in other words, if it's not consistent with God's Word, which our Confessions merely summarize and repeatedly point us back to over and over again) so that I can correct those errors immediately and not lead any of His little ones astray (James 3:1). Also, please be aware that you might also discover that some of the earlier/older pieces I wrote for this blog back in 2013 definitely fall into that "Old Evangelical Adam" category (and they don't have a disclaimer like this) since I was a "Lutheran-In-Name-Only" at the time and was completely oblivious to the fact that a Christian "Book of Concord" even existed (Small/Large Catechism? What's that!?!). This knowledge of the Lutheran basics was completely foreign to me even though I was baptized, confirmed, and married in an LCMS church! So, there are some entries that are a little "out there" so-to-speak since the subject matter was also heavy influenced by those old beliefs of mine. I know that now and I'm still learning. Anyway, I decided to leave those published posts up on this website and in cyberspace only because they are not blasphemous/heretical, because I now have this disclaimer, and only to demonstrate the continuing work of Christ and the Holy Spirit in my life (Hebrews 12:2; Philippians 1:6). Most importantly, please know that any time I engage in commenting on and/or interpreting a specific portion of the holy Scriptures, it will always closely follow the verse-by-verse footnotes from my Lutheran Study Bible and/or include references to the Book of Concord unless otherwise noted. Typically, I defer to what other Lutheran Pastors both past and present have already preached and taught about such passages since they are the called and ordained under-shepherds of our souls here on earth. Finally, I'm going to apologize ahead of time for the length of most entries (this disclaimer/note is a perfect example of what I mean! haha). I'm well aware that blogs should be short, sweet, and to the point, but I've never been one to follow the rules when it comes to writing. Besides, this website is more like a "Christian Dude's Diary" in the sense that everything I write about and share publicly isn't always what's "popular" or "#trending" at the time, but is instead all the things that I'm studying myself at the moment. For better or for worse, these posts tend to be much longer than most blog entries you'll find elsewhere only because I try to pack as much info as possible into a single piece so that I can refer to it again and again over time if I need to (and so that it can be a valuable resource for others -- if possible, a "One-Stop-Shop" of sorts). Thank you for stopping by and thank you in advance for your time, help, and understanding. Feel free to comment/email me at any time. Grace and peace to you and yours!