What was the motivation of the first murder in world history? Was he really guilty? Did he have a good excuse to acquit himself?
The Torah records the murder of Hevel by his brother Kayin, which occurred after Hashem accepted Hevel’s sacrifice but not Kayin’s. The Medrish Tanchuma (paragraph 9) goes into a lot more detail of what actually transpired.
Here is a depiction of the account based on one of the views in the Medrish with additional information from its commentary, the Etz Yosef: Kayin and Hevel were 40 years old at the time. Kayin sacrificed flax seed (i.e. linen) and Hevel sacrificed a first born of his sheep, therefore wool and linen became forbidden as a mixture as it says, “You shall not wear shaatnez, wool and linen together” (Devarim 22:11). And Hashem said it is inappropriate to mix the offering of the sinner with the offering of the innocent, therefore the mixture of wool and linen became forbidden.
After this episode Kayin said to Hevel, “What do you say? Our father has separated himself from our mother and is not having anymore children, and Hashem is angry with him, it’s as if he is dead so why don’t we discuss our inheritance? We can split the whole entire world but since I am the firstborn, I deserve to get a double portion.”
Hevel responded, “If this is halachically true then I will submit to your will”.
Kayin said back, “Thank you and I will include the place where your offering was accepted as in my domain.”
The place, where the alter was, was to be where the Beis Hamikdash would be built, and it is known that the Beis Hamikdash is in the center of the world, therefore when they were splitting the world, and Kayin was going to take a double portion then the Beis Hamikdash would then be in his portion.
Hevel refused to accept this split claiming that the world didn’t have to be split in the center exactly next to each other and therefore he can keep what was already coming to him when Hashem accepted his sacrifice.
Even though the Beis Hamikdash was not built yet they both wanted that location because either they knew the place itself was inherently holy or they were hoping to live long enough for the Beis Hamikdash to be built in their lifetime.
After Hevel’s refusal of the deal a fight ensued and Kayin started chasing Hevel from mountain to valley and from valley to mountain until they grabbed onto each other and Hevel, who was stronger, knocked down Kayin and pinned him to the floor. When Kayin saw the bad fortune he was in he started shrieking, “Hevel my brother don’t do anything wrong to me!” Hevel had mercy and released him. Kayin then got up and killed Hevel, as the Torah says, “And Kayin got up” which implies he had fallen.
As soon as he had killed him, Kayin said to himself, ‘I must run away from my parents, for they will ask me about Hevel, for there is no one else in the world besides him and I.’
Immediately, Hashem appeared to Kayin and said to him, “You can run away from your parents, but you cannot run away from Me… Where is Hevel, your brother? He was merciful upon you and didn’t kill you when you fell under his clutches, but you slipped out and killed him. And how did you kill him? You beat him with a stone on his legs then his arms, for you didn’t know where his soul would come out…until you got to his neck.”
When Hashem had asked where is Hevel your brother, Kayin had responded, “I don’t know, am I my brother’s keeper? You are the guardian of all creatures, and You are asking me where he is?” Then Kayin admitted, “I killed him but You created inside me a yetzer hara (The Etz Yosef points out at this juncture that this is what Kayin meant when he said ‘I don’t know’ meaning I was not in the right state of mind, for temporary insanity entered inside me, which is the power of the Yetzer Hara, the Evil Inclination, and he did it, for a person only sins when he goes temporarily insane, and without knowledge he sins.) You protect everything and You let me kill him, in fact You killed him, for if You would have accepted my offering like You did his, I would not have been jealous of him.” (Click here for Hebrew text.)
After some more intense back and forth between Hashem and Kayin, Kayin admitted to his sin, in a form of repentance and his punishment was downgraded from death on the spot to a lifetime of exile until he himself was accidentally murdered by his blind 7th generation grandson, Lemech, when he was hunting, being lead by his son Tuval Kayin, the real culprit, who Lemech also killed after he realized what his son caused him to do.
Though Kayin does sound like he had some chutzpah, the way he was talking to Hashem, and his underlying motivational bias was jealousy, however it does not seem that the motivation was out right negative jealousy. He wanted a share in the holiest place on earth just as Hevel wanted. This means his motivations were noble, altruistic motivations stemming from a pure drive to be close to Hashem, and maybe even remorse for that ill given offering that he had sacrificed. He was also knocked down first, granted Hevel had mercy on him and didn’t kill him when he easily could have, but Kayin might have felt he had an excuse of self-defense or self-protection, to ensure he would not be killed by his stronger brother. Lastly, why wasn’t his excuse of temporary insanity caused by the Evil Inclination an acceptable excuse? How can he be held responsible for murder, he wasn’t in a right state of mind at the time?!
Hashem’s responded rhetorically, “What did you do?!” Which the Etz Yosef explains to mean, “You did a tremendous thing, for you caused the yetzer hara to control you, for you made him bad!”
We see from here that temporary insanity is no excuse for innocence, on the contrary, that’s the way the Evil Inclination gets everyone to sin. However, it is because we allow the Yetzer Hara to get to that point, that we are held responsible for the actions we do in that temporary state of insanity. It is within our potential power to put the Evil Inclination in check and not allow ourselves to fall into that state of sin. We have the means! We have the tricks and the ability to have self-discipline in order to with stand and overcome the Yetzer Hara we just have to be on guard all the time. We must be sure not to let down our guard even for a moment.