“All those who were listed of the Levites, whom Moses and Aaron and the chiefs of Israel listed, by their clans and their fathers’ houses, from thirty years old up to fifty years old, everyone who could come to do the service of ministry and the service of bearing burdens in the tent of meeting, those listed were 8,580. According to the commandment of the Lord through Moses they were listed, each one with his task of serving or carrying. Thus they were listed by him, as the Lord commanded Moses” (Numbers 4:46-49, ESV).
The Book of Numbers begins at Mount Sinai, where the Israelites have received their laws and covenant from God. Now God has taken up residence among them in the Tabernacle that resides in the middle of their encampment. As they sojourn through the wilderness to take possession of the Promised Land, it will be a major logistical undertaking to mobilize, move and secure the Tabernacle at each layover along their journey.
“Then the Lord said to Moses, ‘When you take a census of the Israelites to count them, each one must pay the Lord a ransom for his life at the time he is counted. Then no plague will come on them when you number them. Each one who crosses over to those already counted is to give a half shekel… This half shekel is an offering to the Lord. All who cross over, those twenty years old or more, are to give an offering to the Lord'” (Exodus 30:13-14, NIV).
The census was actually a way to determine a record of military manpower. But, when Moses enlisted men for military service, he was also to take a ransom from each twenty-year-old or more male and use it for the construction and ministry of the Tabernacle.
“Crossing over to those already counted” literally meant passing over to those who are mustered. It meant joining the ranks of the enlisted men. By passing muster the Israelite male effectively became a soldier in the Israeli militia–the Lord’s army.