"He shall do for her according to the law of daughters" (Exodus 21:9): and what have we now learned about the law of daughters? Rather, this verse comes to teach and is found to be taught itself: just as for this one [the betrothed maidservant], her food, her clothing, and her conjugal rights he may not diminish, so too for a daughter of Israel, her food, her clothing, and her conjugal rights he may not diminish, the words of Rabbi Yoshiyah. Rabbi Yonatan says: Scripture speaks of the Hebrew maidservant. You say so, or is it rather about a daughter of Israel? When it says "if he takes another wife" (Exodus 21:10), behold the daughter of Israel is already mentioned; what then does "according to the law of daughters" teach? Scripture speaks of the Hebrew maidservant.
The Three Duties a Husband Owes Every Wife
Yalkut Shimoni on Torah 320:7
כְּמִשְׁפַּט הַבָּנוֹת יַעֲשֶׂה לָּהּ, וְכִי מַה לָּמַדְנוּ עַל מִשְׁפַּט הַבָּנוֹת מֵעַתָּה, אֶלָּא הֲרֵי זֶה בָּא לְלַמֵּד וְנִמְצָא לָמֵד, מַה זּוֹ שְׁאֵרָהּ כְּסוּתָהּ וְעֹנָתָהּ לֹא יִגְרָע, אַף בַּת יִשְׂרָאֵל שְׁאֵרָהּ כְּסוּתָהּ וְעֹנָתָהּ לֹא יִגְרָע דִּבְרֵי רַבִּי יֹאשִׁיָּה. רַבִּי יוֹנָתָן אוֹמֵר, בְּעִבְרִיָּה הַכָּתוּב מְדַבֵּר. אַתָּה אוֹמֵר כֵּן, אוֹ אֵינוֹ אֶלָּא בְּבַת יִשְׂרָאֵל, כְּשֶׁהוּא אוֹמֵר אִם אַחֶרֶת יִקַּח לוֹ הֲרֵי בַּת יִשְׂרָאֵל (הַכָּתוּב) אָמוּר, מַה תַּלְמוּד לוֹמַר כְּמִשְׁפַּט הַבָּנוֹת, בְּעִבְרִיָּה הַכָּתוּב מְדַבֵּר.