Since God had designated the Levites to be in charge of the tabernacle and its furnishings and to assist the high priest and priests, they were to reside around the tabernacle. Every male descendant of Levi’s three sons more than a month old was numbered. They were assigned their specific locations on the west, south and north sides of the tabernacle. Moses, Aaron and his sons, who were charged with the daily tabernacle services, camped on the east side.
God had specified that the firstborn children of each of the families and the firstborn of their livestock would be His. Instead of taking these firstborn children and livestock from the children of Israel, God chose to use the Levites and their livestock as substitutes. The firstborn males one month and older of the Israelites was counted.