Moshe (Moses) is still on the mountain and receiving the instruction from God about how to build the Tabernacle but in this chapter, God is telling Moshe the procedure He wants Moshe to do to prepare Aharon (Aaron) and his sons for ministry in the Temple. Why does God ask Moshe to this complicated, 7 day ritual? The end of the chapter tell us the punchline. Although Moshe will be doing all of this but it really God will do all the sanctification, not Moshe.

“I will consecrate the tent of meeting and the altar; I will also consecrate Aharon and his sons to minister as priests to Me. I will dwell among the sons of Israel and will be their God. They shall know that I am the LORD their God who brought them out of the land of Egypt, that I might dwell among them; I am the LORD their God.” (Ex. 29:44–46)

The entire purpose of ordaining Aharon in this laborious process is shown at he end of the chapter. Moshe did all this so God could dwell with His people in the Tabernacle and so Aharon and his sons could perform all the duties of the Tabernacle.

Yeshua did what He did so God can dwell with us.