"And if a man acts with intent" (Exodus 21:14). The school of Hezekiah taught: a man acts with intent and can father children, but a minor cannot act with intent and father children. And from where do we know that this word "acts with intent" is a term of cooking or ripening? As it is written, "and Jacob cooked a stew" (Genesis 25:29). Rava said: a minor does not beget, as it says "and if the man has no redeemer" (Numbers 5:8) - and is there a person in Israel who has no redeeming kinsman? Rather, the verse speaks of robbing a convert. And the Merciful One said "a man" - him you must investigate to see whether he has kinsmen or not; a minor you need not investigate, for it is known that he has no offspring to redeem. Abaye raised an objection to him: "a man" (Leviticus 19:20) - I have only a man; from where a boy of nine years and one day with regard to intercourse? Scripture says "and a man." He said to him: he has the capacity but does not produce seed, like grain that has not yet reached a third of its ripening. "And if a man acts with intent" - why is this said? Because it says "And a man who strikes any human life," I might think this includes the intentional and the unintentional killer alike, and others, and the physician who killed, and one who strikes by authority of the court, and one who disciplines his son or his student; Scripture says "and if a man acts with intent," to exclude the unintentional killer; "a man," to exclude the minor; "his fellow," to exclude the others. Issi ben Akiva says: before the giving of the Torah we were warned against the shedding of blood. After the giving of the Torah, instead of being made stricter, they were made more lenient. In truth they said: he is exempt from the laws of flesh and blood, and his judgment is handed over to Heaven. "To kill him by cunning" - to exclude a deaf-mute, an imbecile, and a minor, who do not act with cunning, and to exclude the physician who killed, one who strikes by authority of the court, and one who disciplines his son or his student; for although they act with intent, they do not act with cunning.
When a Man Acts With Intent and Why a Minor Is Exempt
Yalkut Shimoni on Torah 325:1
(שמות כא יד) וְכִי יָזִד אִישׁ, דְּבֵי חִזְקִיָּה תָּנָא, אִישׁ מֵזִיד וּמַזְרִיעַ, וְאֵין קָטָן מֵזִיד וּמַזְרִיעַ. וּמַאי מַשְׁמַע דְּהַאי יָזִד לִישְׁנָא דְּבִשּׁוּלֵי הוּא, דִּכְתִיב (בראשית כה, כט) "וַיָּזֶד יַעֲקֹב נָזִיד". אֲמַר רָבָא, קָטָן אֵינוֹ מוֹלִיד, שֶׁנֶּאֱמַר (במדבר ה, ח) "וְאִם אֵין לָאִישׁ גּוֹאֵל", וְכִי יֵשׁ אָדָם בְּיִשְׂרָאֵל שֶׁאֵין לוֹ גוֹאֵל, אֶלָּא בְּגֶזֶל הַגֵּר הַכָּתוּב מְדַבֵּר, וַאֲמַר רַחֲמָנָא, "אִישׁ" אַתָּה צָרִיךְ לְחַזֵּר עָלָיו אִם יֵשׁ לוֹ גּוֹאֲלִין אִם לֹא, קָטָן אִי אַתָּה צָרִיךְ לְחַזֵּר אַחֲרָיו, בְּיָדוּעַ שֶׁאֵין לוֹ גּוֹאֵל. אֵיתִיבֵיהּ אַבַּיֵּי, (ויקרא יט, כ) אִישׁ, אֵין לִי אֶלָּא אִישׁ, בֶּן תֵּשַׁע שָׁנִים וְיוֹם אֶחָד, לְבִיאָה מִנַּיִן, תַּלְמוּד לוֹמַר "וְאִישׁ". אֲמַר לֵיהּ יֵשׁ לוֹ וְאֵינָהּ מַזְרַעַת, כִּתְבוּאָה שֶׁלֹּא הֵבִיא שְׁלִישׁ דָּמֵי. וְכִי יָזִד, לָמָּה נֶאֱמַר, לְפִי שֶׁנֶּאֱמַר "וְאִישׁ כִּי יַכֶּה כָּל נֶפֶשׁ אָדָם" יָכוֹל בֵּין הַמֵּזִיד וְהַשּׁוֹגֵג וַאֲחֵרִים וְהָרוֹפֵא שֶׁהֵמִית וּמַכֶּה בִּרְשׁוּת בֵּית דִּין וְהָרוֹדֶה בִּבְנוֹ וּבְתַלְמִידוֹ בְּמַשְׁמָע, תַּלְמוּד לוֹמַר וְכִי יָזִד, לְהוֹצִיא אֶת הַשּׁוֹגֵג, אִישׁ, לְהוֹצִיא אֶת הַקָּטָן, רֵעֵהוּ לְהוֹצִיא אֶת הָאֲחֵרִים. אִסִּי בֶּן (יַעֲקֹב) [עֲקִיבָא] אוֹמֵר, קֹדֶם מַתַּן תּוֹרָה הָיִינוּ מֻזְהָרִין עַל שְׁפִיכוּת דָּמִים. אַחַר מַתַּן תּוֹרָה, תַּחַת שֶׁהֻחְמְרוּ, הֵקֵלּוּ. בֶּאֱמֶת אָמְרוּ, פָּטוּר מִדִּינֵי בָּשָׂר וָדָם, וְדִינוֹ מָסוּר לַשָּׁמָיִם. לְהָרְגוֹ בְעָרְמָה, לְהוֹצִיא חֵרֵשׁ שׁוֹטֶה וְקָטָן, שֶׁאֵינָן מַעֲרִימִין, וּלְהוֹצִיא רוֹפֵא שֶׁהֵמִית וְהַמַּכֶּה בִּרְשׁוּת בֵּית דִּין וְהָרוֹדֶה בִּבְנוֹ וּבְתַלְמִידוֹ, אַף עַל פִּי שֶׁהֵן מֵזִידִין, אֲבָל אֵינָן מַעֲרִימִין.