Exodus 25-27 speaks to the plans for the construction of the Tabernacle.
Exodus 28 speaks of the garments the priests would wear.
Exodus 29 speaks to the ordination of the Priests.
Exodus 35-40 speaks to the actual building of the Tabernacle, with it’s completion on the first day of the first month of the second year after Israel left Egypt. This section in Exodus begins with planning, and ends with completion.
Leviticus reaches back before the building of the Tabernacle to discuss in detail the work of the priests, and includes, in chapter 8, a repeat of their ordination. The book ends with details of the holy festivals only briefly mentioned in Exodus 23.
Numbers begins a month after the building of the tabernacle with the census and the arrangement of the tribes around the tabernacle. It then reaches back before the Tabernacle to introduce us to the Levites, those descendants of Levi (but not a part of Aaron’s immediate family) who would be engaged in supporting the work of the Priests. It deals with their work and how it was to be carried out.
Finally, Numbers 7 picks up after the Tabernacle is built, and for the next twelve days, each tribe takes a turn in offering the sacrifices for that day’s service. Chapter 7 is very repetitious. Bible scholar R.K. Harrison tells us why: “The altar was the focal point of daily worship, and it was therefore appropriate that when it was dedicated a representative from every tribe should offer all the regular sacrifices. It set a precedent and demonstrated . . . as strongly as possible that every tribe had an equal stake in the worship of God, and that each was fully committed to the support of the tabernacle and its priesthood.”
The same is true today of the work and worship of the Church. Every member, because he is a part of Christ’s one body, has a responsibility to that body to support it’s health and work.