Reference for Gittin 4:5
מִי שֶׁחֶצְיוֹ עֶבֶד וְחֶצְיוֹ בֶן 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 אִי אֶפְשָׁר, שֶׁכְּבָר חֶצְיוֹ בֶן חוֹרִין. בַּת חוֹרִין אִי אֶפְשָׁר, שֶׁכְּבָר חֶצְיוֹ עָבֶד. יִבָּטֵל, וַהֲלֹא לֹא נִבְרָא הָעוֹלָם אֶלָּא לִפְרִיָּה וְלִרְבִיָּה, שֶׁנֶּאֱמַר (ישעיה מה) לֹא תֹהוּ בְרָאָהּ, לָשֶׁבֶת יְצָרָהּ. אֶלָּא מִפְּנֵי תִקּוּן הָעוֹלָם, כּוֹפִין אֶת רַבּוֹ וְעוֹשֶׂה אוֹתוֹ בֶן חוֹרִין, וְכוֹתֵב שְׁטָר עַל חֲצִי דָמָיו. וְחָזְרוּ בֵית הִלֵּל לְהוֹרוֹת כְּדִבְרֵי בֵית שַׁמָּאי:
If one were half bondsman-half free [as when he were the bondsman of two masters, and one of them freed him], or else, when his master received half of his value from him and freed half of him for that money], he serves his master one day, and himself the other day. These are the words of Beth Hillel. Beth Shammai said to them: "You have 'amended' his master, [who loses nothing], but you have not amended him!" He cannot marry a bondswoman, for he is half-free. He cannot marry a free-woman, for he is half-bondsman. Not to marry — Was the world not created for fruitfulness and multiplication, viz. (Isaiah 45:18): "Not for naught did He create it; to be inhabited did He form it." Rather, because of "the general good" his master is compelled to free him, and he (the servant) writes a bill of debt for half of his value. [The same holds if he were the bondsman of a hundred partners and one of them freed him. All of them are compelled to free him.] And Beth Hillel reversed themselves to rule according to the words of Beth Shammai.