Talmud for Eduyot 1:13
מִי שֶׁחֶצְיוֹ עֶבֶד וְחֶצְיוֹ בֶּן חוֹרִין, עוֹבֵד אֶת רַבּוֹ יוֹם אֶחָד וְאֶת עַצְמוֹ יוֹם אֶחָד, דִּבְרֵי בֵית הִלֵּל. אָמְרוּ לָהֶם בֵּית שַׁמַּאי, תִּקַּנְתֶּם אֶת רַבּוֹ, וְאֶת עַצְמוֹ לֹא תִקַּנְתֶּם. לִשָּׂא שִׁפְחָה, אֵינוֹ יָכוֹל. בַּת חוֹרִין, אֵינוֹ יָכוֹל. לִבָּטֵל, וַהֲלֹא לֹא נִבְרָא הָעוֹלָם אֶלָּא לִפְרִיָּה וּרְבִיָּה, שֶׁנֶּאֱמַר (ישעיה מה), לֹא תֹהוּ בְרָאָהּ לָשֶׁבֶת יְצָרָהּ. אֶלָּא, מִפְּנֵי תִקּוּן הָעוֹלָם, כּוֹפִין אֶת רַבּוֹ וְעוֹשֶׂה אוֹתוֹ בֶן חוֹרִין וְכוֹתֵב שְׁטָר עַל חֲצִי דָמָיו. חָזְרוּ בֵית הִלֵּל לְהוֹרוֹת כְּבֵית שַׁמָּאי:
If one were half-slave, half-free, [as the slave of two partners, who was freed by one of them, or as one whose master received from him half of his (redemption) money, by which half of him was freed], he serves his master one day and himself another day. These are the words of Beth Hillel. Beth Shammai said to them: You have aided his master, [who loses nothing], but you have not aided him! He cannot marry a maidservant, [because of the part of him that is free], and he cannot (marry) a free woman, [because of the part of him that is slave]. Shall he abstain (from marriage)? Was the world not created for having children? viz. (Isaiah 5:18): "Not for naught did He create it; to be settled did He form it!" But, for the world's amendment (tikkun haolam), we force his master to free him, and he writes (his master) a note (of indebtedness) for half his worth. [(The same applies if he were the slave of a hundred partners; all of them are forced to free him)] — whereupon Beth Hillel retracted, to rule in accordance with Beth Shammai.