It was taught: he goes free through tooth and eye and through the extremities of the limbs that do not regenerate. Granted tooth and eye, for they are written explicitly; but the extremities of the limbs, from where do we learn them? [From the words] "like tooth and eye": just as tooth and eye are blemishes that are visible and do not regenerate, so too any blemish that is visible and does not regenerate. And say that tooth and eye are like two verses that come as one [to teach a single matter], and two such verses do not teach [a general rule]? They are both necessary. For had the Merciful One written only "tooth," I would have said even a milk tooth [which regenerates]; therefore the Merciful One wrote "eye." And had He written only "eye," I would have said: just as the eye is created with him, so too only what is created with him [frees the slave], but a tooth would not; therefore it is necessary. And say: "if he strikes" is a generality, "tooth and eye" is a specification; in a generality and a specification, the generality includes only what is in the specification, so tooth and eye yes, but anything else no. [Scripture continues] "he shall send him free," which returns and generalizes; in a generality, a specification, and a generality, you may infer only what resembles the specification. And say: just as the specification is a visible blemish that disables him from his work and does not return, so too any such; yet why was it taught that if he tore at his beard and dislodged a bone from it the slave goes free? [Rather] "he shall send him free" is an amplification. Our Rabbis taught: in all of these the slave goes free and requires a writ of emancipation; these are the words of Rabbi Shimon. Rabbi Meir says he does not require it. Those who decide before the Sages say: the words of Rabbi Tarfon appear correct regarding tooth and eye, which the Torah grants him; and the words of Rabbi Akiva regarding the other limbs, since it is a teaching of the Sages. What is Rabbi Shimon's reasoning? He derives "sending" from "sending" stated of a woman [divorcee]: just as a woman goes out by a document, so too a slave by a document. And Rabbi Meir [reasons]: had it written "he shall send him free" at the end, it would be as you say; now that it writes "to freedom he shall send him," he is as one already free from the start.
Which Wounds Set a Slave Free Forever
Yalkut Shimoni on Torah 339:3
תָּנָא, יוֹצֵא בְּשֵׁן וָעַיִן וּבְרָאשֵׁי אֵבָרִים שֶׁאֵינָן חוֹזְרִין. בִּשְׁלָמָא שֵׁן וְעַיִן, כְּתִיב, אֶלָּא רָאשֵׁי אֵבָרִים מִנָּלָן, כִּי שֵׁן וָעַיִן, מַה שֵׁן וָעַיִן מוּמִין שֶׁבַּגָּלוּי וְאֵינָן חוֹזְרִין, אַף כָּל מוּמִין שֶׁבַּגָּלוּי וְאֵינָן חוֹזְרִין. וְאֵימָא נֵיהֲוֵי שֵׁן וְעַיִן כִּשְׁנֵי כְּתוּבִין הַבָּאִין כְּאֶחָד וְאֵין מְלַמְּדִין, צְרִיכֵי, דְּאִי כָּתַב רַחֲמָנָא שֵׁן, הֲוָה אֲמִינָא אֲפִלּוּ שֵׁן דְּחָלָב, כָּתַב רַחֲמָנָא עַיִן. וְאִי כָּתַב רַחֲמָנָא עַיִן, הֲוָה אֲמִינָא מָה עַיִן שֶׁנִּבְרֵאת עִמּוֹ אַף כָּל שֶׁנִּבְרָא עִמּוֹ אֲבָל שֵׁן לָא, צְרִיכָא. וְאֵימָא כִּי יַכֶּה כְּלָל, שֵׁן וְעַיִן פְּרָט, כְּלָל וּפְרָט אֵין בַּכְּלָל אֶלָּא מַה שֶּׁבַּפְּרָט, שֵׁן וְעַיִן אִין, מִידִי אַחֲרִינָא לָא. לַחָפְשִׁי יְשַׁלְּחֶנּוּ, חָזַר וְכָלַל, כְּלָל וּפְרָט וּכְלָל אִי אַתָּה דָּן אֶלָּא כְּעֵין הַפְּרָט, מַה הַפְּרָט מְפֹרָשׁ מוּמִין שֶׁבַּגָּלוּי וְאֵינָן חוֹזְרִין וְכוּ'. וְאֵימָא מַה הַפְּרָט מְפֹרָשׁ מוּמִין שֶׁבְּגָלוּי וּבָטֵל מִמְּלַאכְתּוֹ וְאֵינוֹ חוֹזֵר, אַף כָּל וְכוּ', אֲלָמָה תַּנְיָא תָּלַשׁ בִּזְקָנוֹ וְדִלְדֵּל בּוֹ עֶצֶם עֶבֶד יוֹצֵא בּוֹ לְחֵרוּת. לַחָפְשִׁי יִשַׁלְּחֶנּוּ, רִבּוּיָא הוּא. אִי רִבּוּיָא הוּא, אֲפִלּוּ הִכָּהוּ עַל יָדוֹ וְצָמְתָה וְסוֹפָהּ לַחֲזֹר, אֲלָמָה תַּנְיָא הִכָּהוּ עַל יָדוֹ וְצָמְתָה וְסוֹפוֹ לַחֲזֹר אֵין עֶבֶד יוֹצֵא בָּהּ לְחֵרוּת. אִם כֵּן שֵׁן וְעַיִן מַאי אַהֲנֵי לֵיהּ. תָּנוּ רַבָּנָן, בְּכֻלָּן עֶבֶד יוֹצֵא בָּהֶן לְחֵרוּת וְצָרִיךְ גֵּט שִׁחְרוּר, דִּבְרֵי רַבִּי שִׁמְעוֹן. רַבִּי מֵאִיר אוֹמֵר, אֵינוֹ צָרִיךְ. רַבִּי אֱלִיעֶזֶר אוֹמֵר, צָרִיךְ. רַבִּי טַרְפוֹן אוֹמֵר, אֵינוֹ צָרִיךְ. הַמַּכְרִיעִין לִפְנֵי חֲכָמִים אוֹמְרִים, נִרְאִין דִּבְרֵי רַבִּי טַרְפוֹן בְּשֵׁן וְעַיִן שֶׁהַתּוֹרָה זָכְתָה לוֹ, וְדִבְרֵי רַבִּי עֲקִיבָא בִּשְׁאַר אֵבָרִים הוֹאִיל וּמִדְרַשׁ חֲכָמִים הוּא. מַאי טַעְמָא דְּרַבִּי שִׁמְעוֹן, יָלִיף שִׁלּוּחַ שִׁלּוּחַ מֵאִשָּׁה, מָה אִשָּׁה בִּשְׁטָר אַף עֶבֶד נַמִי בִּשְׁטָר. וְרַבִּי מֵאִיר, אִי כָּתַב יְשַׁלְּחֶנּוּ חָפְשִׁי לְבַסּוֹף, כִּדְקָאָמְרֵת, הָשְׁתָא דִּכְתִיב לַחָפְשִׁי יְשַׁלְחֶנּוּ הֲוָה לֵיהּ חָפְשִׁי מֵעִיקָרָא.