Bamidbar or Numbers is the culmination of the story of Israel's exodus from oppression in Egypt and their journey to take possession of the land HaShem promised their fathers. As such it draws to a conclusion the themes introduced in Genesis (B'reshit - In the Beginning) and played out in Exodus (Shemot - Names) and Leviticus (Vayikra - and He called): Elohim has promised the Israelites that they shall become a great nation, that they will have a special relationship with Adonai their Elohim, and that they shall take possession of the land of Canaan.
Bamidbar also demonstrates the importance of holiness, faithfulness and trust: despite HaShem's presence and His priests, Israel lacks faith and the possession of the land is left to a new generation.
For just as the new heavens and the new earth that I am making will continue in my presence,” says Adonai, “so will your descendants and your name continue. “Every month on Rosh-Hodesh and every week on Shabbat, everyone living will come to worship in my presence,” says Adonai.