Murder is one of the most heinous—and oldest—crimes in the world. In the very first Torah portion, when the world is only a few days old, we read that Abel is murdered by his very own brother, Cain. Part of what makes this so shocking is that it seems to come out of nowhere. Here is the Torah’s cryptic account:

Now, it came to pass at the end of days that Cain brought of the fruit of the soil an offering to the L‑rd. And Abel, he too brought of the firstborn of his flocks and of their fattest, and the L‑rd turned to Abel and to his offering. But to Cain and to his offering, He did not turn, and it annoyed Cain exceedingly, and his countenance fell. And the L‑rd said to Cain, "Why are you annoyed, and why has your countenance fallen? Is it not so that if you improve, it will be forgiven you? If you do not improve, however, at the entrance, sin is lying, and to you is its longing, but you can rule over it." And Cain spoke to Abel his brother, and it came to pass when they were in the field that Cain rose up against Abel his brother and slew him.1

In short, Abel was a shepherd and Cain was a farmer. Cain brought an offering to G‑d from the fruit of his harvest, and Abel brought from his firstborn sheep. G‑d accepted the offering of Abel, but not that of Cain. Cain was upset, and G‑d spoke to him, letting him know that sin awaited him (in the future) unless he repented. And then, all of a sudden, Cain met Abel in the field and killed him, ostensibly out of jealousy.

But there seems to be more to the story. Right before Cain killed Abel in the field, the verse says, “Cain spoke to Abel his brother”2—yet the Torah does not tell us what this final exchange of words was all about. Could they have argued over something that led to the murder of Abel? The Midrash offers us a number of explanations, each of which represents a different philosophical reason for the sibling rivalry.

Over Inheritance and Property

According to one Midrash, it all boils down to what has caused much strife in families throughout the ages, namely, the division of property and inheritance.

Seeing that they were the only two humans around, Cain and Abel decided to divide “ownership” of the world. One would take all the lands and things that grow from it, while the other would take movable objects such as animals and the like. Thus, one became a farmer and the other a shepherd. It came to pass, however, that Cain said to Abel, “The land you stand on is mine,” while Abel retorted, “What you are wearing is mine." One said: “Strip”; the other retorted: “Fly off the ground.” It was out of this quarrel that Cain rose up and murdered Abel.3

Others say that they both split the lands and the movable objects, but they were quarreling about on whose portion the future Temple should be built.4

Over a Woman

Another explanation is that they were fighting over—what else?—a woman. According to the Midrash, both Cain and Abel were born with twin sisters, whom they married. However, Abel was actually born with two sisters, and they fought over who would marry the extra wife. Cain said he was the oldest and thus it was his right, while Abel claimed that since she was born with him, it was his right.

Over Theology

Cain, upon seeing that his offering was not accepted but his brother’s was, said to Abel, “It appears that G‑d isn’t just and shows favoritism.” Replied Abel, “Heaven forbid that it be as you say; rather, the reason why my offering was accepted was because it was better.” Cain, in turn, replied, “It appears that there is no reward and punishment for good or bad.” Said Abel, “Surely the righteous are rewarded and the wicked punished.” It was from this quarrel that Cain ended up killing Abel.5

In Conclusion

Although the Midrash explains that Cain ultimately killed Abel over either money, a woman or theology, perhaps one reason why the Torah records the incident in a cryptic manner is to teach us an important lesson. Cain may have been jealous that G‑d accepted Abel’s offering, not his, but G‑d explained to him that it was his own fault that his offering wasn’t accepted. His brother's offering did not make his offering better or worse by comparison; the onus was on Cain to better himself. Likewise, we should not be jealous of others; rather, it is up to us to better ourselves.