Komentarz do Wyjścia 12:49

תורה אחת וגו׳ ONE LAW etc. — This is stated in addition to the similar text in v. 48 in order to declare that the proselyte is equal to the native also in respect to all other commands of the Torah (i. e. the preceding text has reference only to the Paschal offering whilst this is a general statement) (Mekhilta d'Rabbi Yishmael 12:49).

Regarding the other mitzvos of the Torah. You might ask: Why should we think converts are different? They are full Jews! Granted that the previous verse needed to equate the convert to the native born regarding bringing the korbon Pesach on the 14th of Nisan, since we might have thought that he brings the korbon Pesach right when he converts. Thus it is written, “Like the native born,” as Rashi explained. But why should converts be different regarding the other mitzvos of the Torah? The answer is: The fact that the Torah needed to equate them regarding the korbon Pesach on the fourteenth [of Nisan] might have led us to say that they are different regarding other mitzvos. (Re”m)

(Exodus 12:49) "One Torah shall there be for the citizen, etc." What is the intent of this? Is it not already written (Ibid. 48) "And he shall be as the citizen of the land"? From "And if there live with you a stranger and he would offer a Pesach to the L rd," I would think that the proselyte is equated with the citizen only in respect to the Pesach. Whence do I derive (the same for) all the mitzvoth of the Torah? From "One Torah shall there be for the citizen and for the stranger."