It was taught: "He shall surely be avenged" (Exodus 21:20). I do not yet know what this vengeance is. When Scripture says, "And I will bring upon you a sword that avenges the vengeance of the covenant" (Leviticus 26:25), and so forth, you learn that vengeance means by the sword. But say it means he should be split apart? Scripture writes, "by the edge of the sword" (Deuteronomy 13:16). But say he should be cut into pieces? Rav Nachman said in the name of Rabbah bar Avuha: the verse states, "You shall love your neighbor as yourself" (Leviticus 19:18) [choose for him a kind death]. We have found that a free man who killed a slave is put to death by the sword; from where do we learn the case of a slave who killed a free man? Is it not an inference from the lesser to the greater: if one is executed by the sword for killing a slave, surely so for a free man, by strangulation. This works for the one who holds strangulation is the lighter death; but for the one who holds strangulation is the more severe death, what can be said? It is derived from what we learned: "And you shall purge the innocent blood" (Deuteronomy 21:9) [from your midst]. Those who shed blood were compared to the heifer whose neck is broken: just as there it is by the neck, so too here at the neck. If so, just as there it is with a cleaver and from the back of the neck, so too here with a cleaver from the back of the neck? Rav Nachman said in the name of Rabbah bar Avuha: "You shall love your neighbor as yourself" [therefore] choose for him a kind death.
Choose a Kind Death From Love Your Neighbor as Yourself
Yalkut Shimoni on Torah 335:1
תַּנְיָא, נָקֹם יִנָּקֵם, נְקִימָה זוֹ אֵינִי יוֹדֵעַ מַה הִיא. כְּשֶׁהוּא אוֹמֵר "וְהֵבֵאתִי עֲלֵיכֶם חֶרֶב נוֹקֶמֶת נְקַם בְּרִית" וְגוֹ'. וְאֵימָא דְּבָרִיז לֵיהּ מִיבְרַז, (דברים יג, טז) "לְפִי חָרֶב" כְּתִיב. וְאֵימָא דְּעָבִיד לֵיהּ גִּיסְטְרָא, אֲמַר רַב נַחְמָן אֲמַר רַבָּה בַּר אָבוּהָ, אֲמַר קְרָא (ויקרא יט, יח) "וְאָהַבְתָּ לְרֵעֲךָ כָּמוֹךָ", בְּרֹר לוֹ מִיתָה יָפָה. אַשְׁכְּחָן בַּר חוֹרִין דְּקְטַל עֶבֶד, עַבְדָּא דְּקְטַל בַּר חוֹרִין, מִנָּלָן, לָאו קַל וָחֹמֶר קְטַל עֶבֶד בְּסַיִף, בַּר חוֹרִין בְּחָנֶק. הַנִיחָא לְמַאן דַּאֲמַר חֶנֶק קַל, אֶלָּא לְמַאן דַּאֲמַר חֶנֶק חָמוּר מַאי אִיכָּא לְמֵימָר. נַפְקָא לֵיהּ מִדִּתְנַן, (דברים כא, ט) "וְאַתָּה תְּבַעֵר הַדָּם הַנָּקִי", הֻקְּשׁוּ שׁוֹפְכֵי דָּמִים לְעֶגְלָה עֲרוּפָה, מַה לְּהַלָּן בְּסַיִף וּמִן הַצַּוָּאר, אַף כָּאן בְּסַיִף וּבְצַוָּאר. אִי מַה לְּהַלָּן בְּקוֹפִיץ וּמִמּוּל עֹרֶף, אַף כָּאן בְּקוֹפִיץ וּמִמּוּל עֹרֶף. אֲמַר רַב נַחְמָן אֲמַר רַבָּה בַּר אָבוּהָ, "וְאָהַבְתָּ לְרֵעַךָ כָּמוֹךְ", בְּרֹר לוֹ מִיתָה יָפָה.