Kayin intended to kill Hevel and was fully cognizant of the consequences of his actions. This approach subdivides as to whether Kayin was guilty of first degree (premeditated) or second degree (unplanned) murder.
"וַיֹּאמֶר קַיִן אֶל הֶבֶל אָחִיו" and Kayin's motivation
– Rashi, R"Y Bekhor Shor, and Ramban all explain that Kayin's words to Hevel facilitated his conspiracy to kill Hevel.1
According to them, Kayin committed first degree murder out of jealousy over his rejected sacrifice. Alternatively, the various opinions in Bereshit Rabbah suggest that it was a separate argument while Kayin and Hevel were already in the field which led to the murder.
– All other Biblical cases of the root "הרג" refer to intentional murder.2
"לֹא יָדַעְתִּי הֲשֹׁמֵר אָחִי אָנֹכִי" – Rashi explains that this is simply a bald-faced lie.
– These commentators must grapple with the question of why Kayin was not punished by death. R. Nechemya in Bereshit Rabbah and Chizkuni suggest that Kayin did not receive the death penalty because his crime was committed before Hashem gave this instruction.3
Alternatively, see Radak
who proposes that Hashem did not want the world to be desolate. Chizkuni also offers a second possibility that Kayin was not killed because he received no warning (התראה) immediately prior to the murder.
"גָּדוֹל עֲוֹנִי מִנְּשֹׂא"
– Ibn Ezra
interpret this as Kayin's admission of sin, and not a protestation of the severity of the punishment. Abarbanel adds that Kayin is acknowledging that he is really deserving of death. Rashi
, on the other hand, views these words as Kayin's appeal to Divine mercy, despite the gravity of his crime.
"כָל מֹצְאִי יַהַרְגֵנִי" – Ramban explains that Kayin is asking that he not die at the hands of wild animals. Abarbanel, though, understands that Kayin is wishing for immediate death.
"כָּל הֹרֵג קַיִן שִׁבְעָתַיִם יֻקָּם"
– According to Rashi
, this verse means that Kayin will receive his due punishment of death in seven generations time.4
Kayin's killing of Hevel was unintentional, either because he struck him without intent to kill or because he had no prior comprehension of the concept of death.
"וַיַּהַרְגֵהוּ" and Kayin's motivation
– According to this position, "וַיַּהַרְגֵהוּ" can also refer to an act committed without full intent. The Akeidat Yitzchak proposes that Kayin's act was mitigated by the fact that it occurred during an altercation, and the Netziv develops the possibility that Kayin was enslaving Hevel and was beating him as a master beats a slave.5
"לֹא יָדַעְתִּי הֲשֹׁמֵר אָחִי אָנֹכִי" – This approach could explain that Kayin was really telling the truth, and having never before encountered death, was unsure of whether Hevel might recover.
Kayin's punishment – These commentators all point out that positing an accidental killing would be the simplest way to account for why Kayin received a punishment of exile similar to that of an unintentional murderer.
"כָל מֹצְאִי יַהַרְגֵנִי" – According to this opinion, Kayin is claiming that he is undeserving of death.
"כָּל הֹרֵג קַיִן שִׁבְעָתַיִם יֻקָּם" – Hashem agrees with Kayin that he is deserving of protection.