"One law shall there be for the native" (Exodus 12:49). Why is this said? Has it not already been said, "And he shall be as one born in the land" (Exodus 12:48)? What does Scripture come to teach by saying "One law shall there be for the native"? Because it says, "And when a stranger shall sojourn with you" (Exodus 12:48), I would know only the Passover offering, in which Scripture made the convert equal to the native. From where do I learn the rest of all the commandments of the Torah? Scripture teaches, saying "One law" [Torah] — the verse comes and makes the convert equal to the native with respect to all the commandments stated in the Torah.
One Torah Binds the Convert to the Native in Every Commandment
Yalkut Shimoni on Torah 212:3
תּוֹרָה אַחַת יִהְיֶה לָאֶזְרָח. לָמָּה נֶאֱמַר, וַהֲרֵי כְּבָר נֶאֱמַר וְהָיָה כְּאֶזְרַח הָאָרֶץ, מַה תַּלְמוּד לוֹמַר תּוֹרָה אַחַת יִהְיֶה לָאֶזְרָח. לְפִי שֶׁהוּא אוֹמֵר וְכִי יָגוּר אִתְּךָ גֵּר אֵין לִי אֶלָּא פֶּסַח שֶׁהִשְׁוָה בּוֹ אֶת הַגֵּר לָאֶזְרָח, שְׁאַר כָּל הַמִּצְוֹת שֶׁבַּתּוֹרָה מִנַּיִן, תַּלְמוּד לוֹמַר תּוֹרָה אַחַת, בָּא הַכָּתוּב וְהִשְׁוָה אֶת הַגֵּר לָאֶזְרָח לְכָל הַמִּצְוֹת הָאֲמוּרוֹת בַּתּוֹרָה.