Sifrei Mitzvot sobre Deuteronômio 17:16

That we have been prohibited from dwelling in the Land of Egypt forever, so that we not learn from their practices and not follow their disgraceful ways. And that is His saying, "You must not return that way again" (Deuteronomy 17:16). And this prohibition was already repeated three times: They said in the Gemara (Yerushalmi Sukkah 4:1 ), "In three places did the Holy One, blessed be He, warn Israel not to return to Egypt; and at three times did they return and get punished from them." Indeed one of the three places is that which we mentioned. The second is, "by a route which I told you, you should not see again" (Deuteronomy 28:68). And the third is, "for Egypt which you have seen this day - you will never again see them" (Exodus 14:13). Even though it appears from the words that it is narrative, the tradition comes [to teach that] it is a prohibition. And it has already been explained in the Gemara, Sukkah (Sukkah 51b), that Alexandria is from the cities in which it is forbidden to dwell. And [from the Sea of] Alexandria, the measurement of the perimeter of Egypt is four hundred parasangs by four hundred parasangs - and that is the total of the Land of Egypt in which it is forbidden to dwell. But it is permissible to travel in it for business, or to pass through to a different land. And in explanation, they said in the Yerushalmi (Yerushalmi Sanhedrin, Chapter 10 at the end), "You may not return for living, but you may return for business and to conquer the land." (See Parashat Shoftim; Mishneh Torah, Kings and Wars 5.)