Verses 4-9:
This is not the same as the ritual described in Ex 29:1-44. That was the occasion of the consecration of Aaron and his sons as priests. The present text prescribes the public cleansing of all the Levites for the services they were to render about the Tabernacle.
"The water of purifying" is literally, "the water of offering for error or sin," from chattaah. This was not the same as the "water of separation," from the Red Heifer offering, Nu 19:9. It was likely water from the brazen Laver which stood before the Tabernacle door, see Nu 5:17.
All the male Levites were to be shaven completely, then they were to wash their clothes and completely bathe.
The next step was to offer sacrifices:
(1) A young bullock, with a food (bread) offering.
(2) A Sin Offering, consisting of a young bullock, Le 4:3-12.
Those charged with the Tabernacle service were subject to sin, the same as the rest of Israel. They must offer sacrifices for their guilt. This symbolizes the trait of God’s children today, who must daily seek cleansing from sin’s defilement, see 1Jo 1:7-2:2.