Halakhah for Genesis 4:15
וַיֹּ֧אמֶר ל֣וֹ יְהוָ֗ה לָכֵן֙ כָּל־הֹרֵ֣ג קַ֔יִן שִׁבְעָתַ֖יִם יֻקָּ֑ם וַיָּ֨שֶׂם יְהוָ֤ה לְקַ֙יִן֙ א֔וֹת לְבִלְתִּ֥י הַכּוֹת־אֹת֖וֹ כָּל־מֹצְאֽוֹ׃
And the LORD said unto him: ‘Therefore whosoever slayeth Cain, vengeance shall be taken on him sevenfold.’ And the LORD set a sign for Cain, lest any finding him should smite him.
Contemporary Halakhic Problems, Vol III
And the Lord said unto him, "Therefore whosoever slayeth Cain, vengence shall be taken on him sevenfold" (Genesis 4:15). R. Nehemiah said, "The punishment of Cain is not as the punishment of other murderers. Cain killed but he had none from whom to learn [the enormity of his crime]. [But] henceforth whosoever slayeth Cain shall be slain."
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