According to Rebbi in Tractate Shabbat, the parasha of "Va-yehi binsoa" is the dividing point of Sefer Bamidbar. In fact, Rebbi goes even farther, considering the sections of Bamidbar before and after this parasha as distinct books. A quick overview of Bamidbar is sufficient to reveal the sharp contrast that underlies Rebbi's position and a glimpse into the ideal purpose of Sefer Bamidbar - a profound truth about the essence of Am Yisrael and their relationship to God. 

Courtesy of the Virtual Beit Midrash, Yeshivat Har Etzion