"You shall never again return that way"Deuteronomy 17:16.

We are forbidden from dwelling in the land of Egypt, so that we do not learn their heretical ways nor their depraved lifestyle that the Torah decries. Alexandria, too, is part of the boundaries of Egypt that we may not live in. From the Sea of Alexandria we measure 400 parsah [a parsah is approximately four kilometers] to the length and breadth—and that is the boundary of the Land of Egypt that we may not dwell in.

The prohibition only applies to settling in Egypt. It is, however, permitted to travel to Egypt for business purposes, or to annex [parts of it to Israel].