Bereshit 4 describes the first murder in history, the events which led up to it, and its aftermath. The story opens with the birth of Kayin and Hevel and their choice of occupations. It proceeds to describe their sacrifices, and Hashem's acceptance of Hevel's offering and simultaneous rejection of Kayin's. The Torah, though, does not provide an explicit explanation for Hashem's preference, leaving the reader to wonder about its apparent arbitrariness. Targum Pseudo-Jonathan, in fact, portrays Kayin as upset about this very issue:
Kayin answered and said to Abel: I see that the world has been created through mercy, but it is not ordered according to the fruit of good deeds, and that there is partiality in judgment. Otherwise, why was your offering accepted in favor whereas my offering was not accepted from me with favor?
Consequently, Kayin concludes:
There is no judgment, no judge, no other world; there is no fair reward given to the righteous, nor punishment exacted from the wicked.
In the continuation of the story Hashem appears to reprove Kayin, suggesting that he has room to improve:
(ו) וַיֹּאמֶר י״י אֶל קָיִן לָמָּה חָרָה לָךְ וְלָמָּה נָפְלוּ פָנֶיךָ. (ז) הֲלוֹא אִם תֵּיטִיב שְׂאֵת וְאִם לֹא תֵיטִיב לַפֶּתַח חַטָּאת רֹבֵץ וְאֵלֶיךָ תְּשׁוּקָתוֹ וְאַתָּה תִּמְשׇׁל בּוֹ.
(6) Hashem said to Cain, “Why are you angry, and why has your face fallen? (7) If you do well, will you not be uplifted? And if you do not do well, sin crouches at the door. Its desire is for you, but you shall rule over it.”
This rebuke, though, is replete with both lexical and syntactic ambiguities, leaving the reader once again unclear as to Hashem's message. Where do the different clauses of verse 7 begin and end? What does the word "שְׂאֵת" mean? How should we interpret the phrase "לַפֶּתַח חַטָּאת רֹבֵץ"? Is Hashem telling Kayin to improve his actions or his sacrifice? How do Hashem's words relate to His previous rejection of the offering?