Ambrosiaster, Questions on the Old and New Testaments:
QUESTION 5. WHY WAS THE SACRIFICE OF ABEL APPROVED OF GOD, AND THAT OF CAIN REFUSED? — One can conclude from the terms alone of this narrative that the truth of history is not veiled by any literary artifice. The Holy Scripture tells us here clearly that Abel was prudent and religious, while Cain was negligent and careless, and by the same had much less religion. Abel therefore chooses the best sheep of his flock to offer them to his Creator. By offering God the first fruits of the possessions he had made, he testified of God's excellence and deep submission, he testified his feelings of respect and adoration, and acknowledged that God was the author of all things. Cain, guided by coarser sentiments, could not offer God a similar sacrifice. When he was plunged into the things of the earth, he could not raise the eyes of his soul to heaven to consider what might be worthy of his Creator, and he offered to God the most common fruits of the earth. It is in this also that the Jews lacked righteousness. For the Lord has often reproached them that they are inconsiderately charging on his altar victims even unworthy of being offered to men. "You offer me," said he, "sightless or blind victims, I will not receive them from your hands; Offer them to your master or chief if they please him. (Mal. 1:8)” Everyone agrees, indeed, that one must offer what is most excellent to a person of higher dignity. The Lord therefore rejected Cain's gifts and said to him, "Why are you angry and why is your face sad? If you do your offering with righteousness, but you do not have it in the choice of your gifts, you sin. Stay at rest. Your offering comes to you and you are the master of it. (Gen. 4:6). You see that it was the choice of the gift which rendered it, usable. He was not able to discern what was worthy of God, and reserved the best fruits for his use. It is not therefore the offering he has made that God reproaches Cain, but the unworthy presents he offers him. And he is not even condemned for this fact, but because in spite of this warning he would not correct his conduct. "This offering comes to you, and you are the master of it,” (Ibid., 7), that is, those gifts that I reject become your property again. He wants to teach him what to do in the future. Cain conceived a violent jealousy against his brother. This man of iniquity put to death the first righteous man, and thus gave men the example of crime. In fact, this profound jealousy blinded him to the point that not only did he not give thanks to God, who, far from punishing him as guilty, taught him to correct his conduct, but that he fell into a far more enormous crime which attracted his just condemnation. The imprudent conduct of the Cain fratricide resembles that of that wretched servant, who, ungrateful for the forgiveness he had just received from his master, wanted to acquit his companion, and thus deserved to be condemned without excuse, and for the fault which had been forgiven him, and for his cruelty to his fellowman (Matt. 18:28). Nevertheless, Cain was not condemned at once; he was left on earth to be confounded and terrified by his crime, and to facilitate the way of repentance and forgiveness. And as he was afraid of being put to death for the crime he had committed, he said to the Lord, "My iniquity is too great for me to be forsaken; If you reject me today from the face of the earth, I will escape from all eyes, I will be wandering and groaning on earth, and whoever finds me will kill me (Gen. 4:13). Cain, afraid of the condemnation of the just Judge, fears that this abandonment of the Lord forces him to flee the eyes of men, certain that it is that he who has against him an angry God must fear to be put to death by the men. But what does the Lord answer? "It will not be so," said he, "that is to say, I will not let you go, you who do not deserve to live, that you may fall under the blows of your likes, but so that you may spend your life in groans, in fear, and in alarms, as a punishment for the evil example which you first gave on earth, and seeing that the earth does not respond by your productiveness to your labors. He, he adds, who will kill Cain will be punished seven times (Gen. 4:24). This sentence proves the justice of Cain's condemnation. When he saw this law given with that threatening sanction which forbade imitation of his criminal conduct, he knew the whole extent of the crime he had committed, and his fears increased. God threatens to punish seven times as great a punishment, so that by understanding how great the crime of Cain was before the promulgation of a positive law, he knew that he was incurring punishment seven times more severe if he was guilty of it, that is to say that knowledge of the law would add six degrees more to the punishment which Cain had deserved, and that this punishment would be literally sevenfold. This same number also represents the reward of those who have left everything to follow the Lord, and who, in addition, will receive eternal life in the other world. This is the sign that the Lord put on Cain, so that whoever would find him would not do so (Ibid. 15). By virtue of this law which has been brought against the murder, every man who has committed a murder, because all murder is a homicide, would be seven times more guilty than Cain. God wanted the fear of such severe punishment to stop those who would be tempted to commit such a crime. (pp. 51-53)
