Chapter eight records what God spoke to Moses at the end of chapter seven. God’s first instruction was that the lampstand was to be focused in such a way that it did not simply light a general area but rather the space in front of the lampstand (Numbers 8:1-4).
God’s second command, and the majority of the chapter, dealt with the ordination of the Levites to service (Numbers 8:5-22). This goes into greater detail than chapters three and four. A key difference between the ordination of the priests and the Levites is that the leaders of the people were involved with the Levites. Because they were the substitutes for the firstborns of the nation, to be separated to God for ministry, the people participated in their dedication ceremony.
There seems to be a discrepancy between Numbers 8:23-26 and Numbers 4:47, where God had Moses count the Levites between the ages of 30 and 50 as those who could carry the tabernacle pieces. Here God determined that those “the age of twenty-five years and upward one may begin to join the company in the work of the tent of meeting,” but they had to retire at the age of fifty. The probable solution is that the first five years were a type of apprenticeship, during which they could “join…in the work of” the tabernacle, but they could not yet participate in carrying it.