In the third aliyah of Parshas Bamidbar, the configuration of the camp of each shevet (tribe) is discussed. This arrangement around the mishkan was the same set up that Yaakov instructed his children to use when they carried his casket out of Mitzrayim. All of Yaakov's children were unified in serving Hashem, unlike the children of Avraham and Yitzchok. This unity is essential for Hashem's presence to be among us, along with the purity that Yosef demonstrated when he escaped from the possibility of immorality. The aron (casket) of Yaakov and the aron of Yosef teach important lessons as we prepare to accept the Torah-lessons of unity and purity.