Since when is a woman who inherits forbidden to marry into a different tribe than that of her father?
Why was the Torah not similarly concerned regarding an heiress who was already married, or a woman whose father or brothers would die later (leaving behind no sons) after she already married into a different tribe?
Ramban #1: The Torah was only concerned about something that was rectifiable, which those cases were not. And it did not want to change the laws of inheritance in such a case by prohibiting her husband or her son from inheriting her.
Ramban #2: Pasuk 5 and Pasuk 6 are talking about two different Mitzvos. 1 Pasuk 5 is a prohibition against an heiress marrying into a different tribe, whereas Pasuk 6 teaches that if a woman married into a different tribe and then inherited property, her sons or husband do not inherit her. 2
Why was "Lo Sisov Nachalah" said to that generation. What is the reason?