Sforno on Numbers 36:2/ספורנו על במדבר ל״ו:ב׳

1בנחלה בגורל, if a tribe would occupy land belonging to that of another tribe the purpose of sharing out the land by lottery would not have been carried out. [the Torah speaks of the daughters of Tzelofchod possibly marrying out of their tribe and their ancestral heritage therefore becoming part of another tribe, that of their husbands. Ed.]