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וְהָאֱלֹהִי”ם יְבַקֵּשׁ אֶת נִרְדָּף, זֶה הֶבֶל שֶׁהוּא נִרְדַּף מִקַּיִן, וְקָם קַיִן וְהָרַג אוֹתוֹ, זֶהוּ שֶׁכָּתוּב וַיָּקָם קַיִן אֶל הֶבֶל אָחִיו וַיַּהַרְגֵהוּ, וַיָּקָם וַדַּאי, שֶׁהָיָה הֶבֶל עָלָיו, וְקָם קַיִן וַיַּהַרְגֵהוּ. קַיִן נִקְרָא עַל שֵׁם שֶׁקִּנֵּא לְאָחִיו, מִשּׁוּם שֶׁרָאָה כְבוֹדוֹ וְכֹחוֹ לְמַעְלָה, שֶׁקָּרְבָּנוֹ הִתְעַלָּה לְמָקוֹם שֶׁל עַתִּיק הַיָּמִים, שֶׁנֶּאֱמַר בּוֹ וְעַתִּיק הַיָּמִים יוֹשֵׁב וְכוּ’, וְקָרְבָּנוֹ הָיָה מִבְּכוֹרוֹת צֹאנוֹ וְהִתְקַבֵּל לוֹ בְּרָצוֹן.

אָמַר לוֹ, אִם כֵּן שֶׁקָּרְבָּנוֹ הִתְקַבֵּל, לָמָּה נִתַּן כֹּחַ לְקַיִן לְהָרְגוֹ? (בִּגְלַל זֶה יֵשׁ הֶבֶל אֲשֶׁר נַעֲשָׂה עַל הָאָרֶץ וְגוֹמֵר, לָמָּה?) אָמַר לוֹ, כָּאן וַדַּאי יֵשׁ סוֹד עֶלְיוֹן, שֶׁהוּא הָיָה בְדַרְגָּה שֶׁל עֵץ הַדַּעַת טוֹב וָרָע שֶׁחָטָא בוֹ, וּבְמַה שֶּׁחָטָא בוֹ קִבֵּל עָנְשׁוֹ בָּעוֹלָם הַזֶּה, וּבְאוֹתוֹ קָרְבָּן שֶׁהִתְקַבֵּל מִמֶּנּוּ, נִצַּל מֵעֹנֶשׁ שֶׁל אוֹתוֹ הָעוֹלָם, שֶׁשְּׁנֵי עֳנָשִׁים הָיָה מְחֻיָּב, אֶחָד לְמַעְלָה וְאֶחָד לְמַטָּה, זֶהוּ שֶׁכָּתוּב כִּי בְּיוֹם אֲכָלְךָ מִמֶּנּוּ מוֹת תָּמוּת. אָמַר לוֹ, וַהֲרֵי אָדָם הָיָה שֶׁחָטָא בָּעֵץ הַזֶּה? אָמַר לוֹ, מַעֲשֵׂה אָבִיו הָיָה לוֹ וּמֵת. אָמַר לוֹ, כִּי בְּיוֹם אֲכָלְךָ מִמֶּנּוּ מוֹת תָּמוּת כָּתוּב. אָמַר לוֹ, בְּאוֹתוֹ הַיּוֹם הֵצִיץ וּמֵת.

Tikkun 69 – 21

Genesis 4:4,5
“וְהֶבֶל הֵבִיא גַם-הוּא מִבְּכֹרוֹת צֹאנוֹ, וּמֵחֶלְבֵהֶן; וַיִּשַׁע יְהוָה, אֶל-הֶבֶל וְאֶל-מִנְחָתוֹ.;
וְאֶל-קַיִן וְאֶל-מִנְחָתוֹ, לֹא שָׁעָה; וַיִּחַר לְקַיִן מְאֹד, וַיִּפְּלוּ פָּנָיו ”
“And Abel, he also brought of the firstlings of his flock and of the fat thereof. And the LORD had respect unto Abel and to his offering; but unto Cain and to his offering He had not respect. And Cain was very wroth, and his countenance fell”

Cain’s name קין has the same root of קינא, which means jealousy. It reveals the reason behind killing his brother.

Abel’s offering from the first born of his flock was an act that connected him to the level of Keter. Cain’s offering was from the fruit of the earth, which was a lower level.
He couldn’t do better because he was the first born and was connected to the sin of his parents. He was also ‘contaminated’ with the seed and consciousness of the Snake.

He was born with one soul mate while his brother was born with two. With the offering Abel raised himself to the higher level of Keter and Cain couldn’t restrict on his jealousy.

Cain inherited the consciousness of the Snake in his blood. With that relation he knew how stop Abel’s connection to the light. He spoke to Abel, brought him to his level of Malchut where he could rise above him and killed him.

Genesis 4:8
“וַיֹּאמֶר קַיִן, אֶל-הֶבֶל אָחִיו; וַיְהִי בִּהְיוֹתָם בַּשָּׂדֶה, וַיָּקָם קַיִן אֶל-הֶבֶל אָחִיו וַיַּהַרְגֵהוּ”
“And Cain spoke unto Abel his brother (Cain connected to Abel). And it came to pass, when they were in the field (down at Malchut level), that Cain rose up (Cain had the upper hand in the Malchut level) against Abel his brother, and slew him (disconnect him from the light).”

Sibling rivalry is part of human consciousness from the moment of creation. The cause is the desire to connect back to the light on a higher level. The family tree starts with the parents and each of the children want to be close to the top regardless of age or size. The little one may fight fiercely to be the first and the older one may flush his little brother down the toilet if he could. The cause is a spiritual desire that can not be fixed with toys or money. Parents should understand it and remedy the situation by bringing balance with love and special attention.