G‑d tells Moses to take a census—a count—of all the people who can be part of the army, which means all men between the ages of twenty and sixty. Each of the twelve tribes had a leader—a nassi--who helped Moses do the counting.

This is the list of the tribes and their leaders, and the number of people in each tribe.

Tribe Nassi Population
Reuben Elitzur 46,500
Shimon Shelumiel 59,300
Judah Nachshon 74,600
Issachar Nethanel 54,400
Zebulun Eliab 57,400
Menasseh Gamliel 32,200
Benjamin Abidan 35,400
Dan Achi'ezer 62,700
Asher Pagiel 41,500
Gad Eliasaph 45,650
Naphtali Achirah 53,400
Ephraim Elishamah 40,500

The tribe of Levi was counted separately. Counting all males from one month and older, there were 22,300.

Next is discussed how the People of Israel camped and traveled in the desert. When the Jews had to leave their encampment and begin traveling, the Levites would take apart the Mishkan (the Tabernacle that the Jews built), carry it to wherever the next camp was, and set it up again. The camp was arranged like this: In the center was the Mishkan. Around the Mishkan was the camp of the Levites, divided into three groups. The Kehatites, who carried the Mishkan's vessels (the altar, ark, menorah, etc.), camped to its south. The Gershonites, who carried the curtains and roof coverings, were to the west, and the sons of Merrari, who carried the walls and pillars, camped to the north. In front of the Mishkan's entranceway in the east were the tents of Moses, Aaron, and Aaron's sons.

Around the Levites were camped the rest of the People of Israel, in four groups. To the east were Judah, Issachar, and Zebulun; to the south, Reuben, Shimon, and Gad; to the west, Ephraim, Menasseh, and Benjamin; and to the north, Dan, Asher, and Naphtali.

Next is discussed the children of Aaron, the Kohanim, and the Levites, who did the service in the Mishkan. Originally, the firstborns from each family were supposed to do the service, but when they sinned with the golden calf they lost this privilege and it was given instead to the Levites.