The ceremony to make the Levites ceremonially clean involved sprinkling with water, shaving all hair, and wearing clean clothes. This was similar to ceremonies for cleansing from ceremonial impurity.
water of purification: This phrase appears only here. The sprinkling symbolized washing away sin and had symbolic importance similar to later Jewish washings and Christian baptism. This water might have been the same as the mixture with ashes from the red heifer that removed sin (see 19:9; also Hebrews 9:13).
Shaving their entire body was also part of being declared ceremonially clean from the ceremonial impurity of polluting diseases (Leviticus 14:8).
Washing clothes was part of all cleansing from ceremonial impurity (for example, Leviticus 15:5–27).