Bible Notes Online - Numbers 8 - ESV
Commentary

v1-4: The lamps were to be kept lit, giving light to the whole Tabernacle, there being no other source of light inside. Eleazar shared in responsibility for the lamp stand, see 4.16.

v10-11: The Levites were an offering to God from the people; and they were set apart by the people to serve God, "the Levites will be mine" (v14).

The wave offering (in Lev 8, 10) was an offering of consecration; it was also part of the peace offering (Lev 7.28-34). The Levites were thus an offering to the Lord, also v13, 21. Is not the Christian similarly one who is offered to the Lord, and belongs to Him.

v16-18: The Scripture is clear that the Lord took the Levites in place of the first born, as being set apart for Himself.

v19: The Levites were also given to Aaron, to serve in the Tabernacle, and to make atonement for the people.

v22: Having been purified, the Levites were able to commence their service.