One who strikes his fellow, whether with a stone or with a fist, and they assessed him as likely to die, and then he improved from his prior condition, and afterward he grew worse and died: [the striker] is liable. But Rabbi Nechemiah says he is exempt. Our Rabbis taught: Rabbi Nechemiah expounded this verse: "if he rise again and walk abroad upon his staff, then shall he that struck him be clear" (Exodus 21:19). Now could it enter your mind that this man walks on his feet in the marketplace and yet that man [the striker] is put to death? Rather, this refers to one whom they assessed as likely to die, and he improved from his prior condition, and afterward grew worse and died, that [the striker] is exempt. And the Rabbis, this phrase "then shall he that struck him be clear," what do they expound from it? It teaches that they imprison him. And Rabbi Nechemiah, from where does he derive imprisonment? He learns it from the wood-gatherer. And the Rabbis: the wood-gatherer was certainly liable to death, and it was only Moses who did not know what his sentence was; this excludes our case, where we do not know whether he is liable to death at all. And Rabbi Nechemiah learns it from the blasphemer, where it was not known that he was liable to death, and they imprisoned him. And the Rabbis: the blasphemer was a ruling for that hour only, as it was taught: Moses our teacher knew that the wood-gatherer was subject to death, as it is said "those who profane it shall surely be put to death" (Exodus 31:14), but he did not know by which death he was to be killed, as it is said "for it had not been declared what should be done to him" (Numbers 15:34); but concerning the blasphemer it says only "to declare," for Moses our teacher did not know whether he was liable to death at all. Granted according to Rabbi Nechemiah, this is why two assessments are written, one [where] they assessed him as likely to die and he lived, and one [where] they assessed him as likely to die and he improved; but according to the Rabbis, and so on. And Rabbi Nechemiah: a case where they assessed him as likely to live and he died needs no verse, for he had already left the court innocent.
Reassessing the Wound When the Victim Worsens and Dies
Yalkut Shimoni on Torah 331:6
הַמַּכֶּה אֶת חֲבֵרוֹ בֵּין בְּאֶבֶן בֵּין בְּאֶגְרֹף, וַאֲמָדוּהוּ לְמִיתָה, וְהוּקַל מִמַּה שֶּׁהָיָה, וּלְאַחַר מִכָּאן הִכְבִּיד וּמֵת, חַיָּב. וְרַבִּי נְחֶמְיָה אָמַר, פָּטוּר. תָּנוּ רַבָּנָן, אֶת זוֹ דָּרַשׁ רַבִּי נְחֶמְיָה, אִם יָקוּם וְהִתְהַלֵּךְ בַּחוּץ עַל מִשְׁעַנְתּוֹ וְנִקָּה הַמַּכֶּה, וְכִי תַּעֲלֶה עַל דַּעְתְּךָ שֶׁזֶּה מְהַלֵּךְ בְּרַגְלָיו בַּשּׁוּק וְזֶה נֶהֱרָג. אֶלָּא זֶה שֶׁאֲמָדוּהוּ לְמִיתָה, וְהֵקֵל מִמַּה שֶּׁהָיָה, וּלְאַחַר מִכָּאן הִכְבִּיד וּמֵת, שֶׁהוּא פָּטוּר. וְרַבָּנָן, הַאי וְנִקָּה הַמַּכֶּה מַאי דָּרְשֵׁי בֵּיהּ, מְלַמֵּד שֶׁחוֹבְשִׁין אוֹתוֹ. וְרַבִּי נְחֶמְיָה, חֲבִישָׁה מִנָּא לֵיהּ, יָלִיף מִמְּקוֹשֵׁשׁ. וְרַבָּנָן, מְקוֹשֵׁשׁ בַּר קְטָלָא הוּא, וּמֹשֶׁה הוּא דְּלָא הֲוָה יָדַע מַאי דִּינֵיהּ, לַאֲפוּקֵי הַאי דְּלָא יַדְעִינָן אִי בַּר קְטָלָא הוּא. וְרַבִּי נְחֶמְיָה, יָלִיף מִמְּגַדֵּף, דֶּלָא הֲוָה יָדַע דְּבַר קְטָלָא הוּא וַחֲבָשׁוּהוּ. וְרַבָּנָן, מְגַדֵּף הוֹרָאַת שָׁעָה הָיְתָה, כִּדְתַּנְיָא, יוֹדֵעַ הָיָה מֹשֶׁה רַבֵּנוּ שֶׁהַמְּקוֹשֵׁשׁ בְּמִיתָה, שֶׁנֶּאֱמַר (שמות לא, יד) "מְחַלְלֶיהָ מוֹת יוּמָת", אֲבָל לֹא הָיָה יוֹדֵעַ בְּאֵיזוֹ מִיתָה הוּא נֶהֱרָג, שֶׁנֶּאֱמַר (במדבר טו, לד) "כִּי לֹא פֹרַשׁ מַה יֵּעָשֶׂה לוֹ", אֲבָל מְגַדֵּף לֹא נֶאֱמַר אֶלָּא "לִפְרֹשׁ", שֶׁלֹּא הָיָה יוֹדֵעַ מֹשֶׁה רַבֵּנוּ אִם בֶּן מִיתָה הוּא כָּל עִקָּר אִם לָאו. בִּשְׁלָמָא לְרַבִּי נְחֶמְיָה, הַיְינוּ דִּכְתִיב תְּרֵי אוּמְדְנֵי, חַד אֲמָדוּהוּ לְמִיתָה וְחָיָה וְחַד אֲמָדוּהוּ לְמִיתָה וְהֵקֵל, אֶלָּא לְרַבָּנָן וְכוּ'. וְרַבִּי נְחֶמְיָה, אֲמָדוּהוּ לְחַיִּים וּמֵת לָא צְרִיכָא קְרָא, שֶׁהֲרֵי יָצָא מִבֵּית דִּין זַכַּאי.