Bible Notes Online - Numbers 1 - ESV
Commentary

v1: 2nd year, 2nd month, 1st day; only one month after Ex 40.17, when the Tabernacle had been raised up. The Israelites had remained at Sinai, as Moses had explained God's standards to them. They only departed from Sinai on the 20th day, see 10.11-12.

v2-4: In Leviticus, the worship of God was organised; here in Numbers, the people of God are organised. In particular, they are organised to fight. This reflects the enmity between God's people and all others.

v5-16: Moses and Aaron were assisted by one man from each tribe; this is shared leadership. Each one is listed, and his father named, as is normal for Jewish tradition. In this way, each man was qualified for the task. These were men respected, see Ex 18.21-22, and they made Moses' burden lighter.

v17-18: They recited their ancestry; for the Christian, this is a 'testimony'; see Ezra 2.59-63.

v20-46: All who were able to fight; they could not enter and enjoy the promised land without fighting. The people were listed by tribe; Reuben, 46,500; Simeon, 59,300; Gad, 45,650; Judah, 74,600; Issachar, 54,400; Zebulun, 57,400; Ephraim, son of Joseph, 40,500; Manasseh, son of Joseph, 32,200; Benjamin, 35,400; Dan, 62,700; Asher, 41,500; Naphtali, 53,400.

The separation of Ephraim and Manasseh into two tribes fulfilled Gen 48.5, 19, and the younger brother had already become the greater.

v46: The total number was 603,550, men under 20 years of age; thus the total number of people including women and children must have been between 1.5 and 2 million.

v47-49: Levi was not numbered for battle, for their appointed task was the service of the Tabernacle.

v52: Each tribe had its own standard. Each one was, presumably, different, indicating the different identity of the tribes.

In 2.3, 10, 18, 25, each group of three tribes had its own standard; the three tribes, for example, under Judah, camped under Judah's standard.

v53: The Levites camped immediately around the Tabernacle, with the other tribes surrounding them, see 2.2.