Charles Ellicott Commentary Nehemiah 12:30

"And the priests and the Levites purified themselves; and they purified the people, and the gates, and the wall." — Nehemiah 12:30 (ASV)

Purified themselves. —Before consecration to God there must be purification from defilement. It is made emphatic that both priests and Levites purified themselves, that is, by offerings and ablutions (Compare to 2 Chronicles 29:15; Ezra 6:20): the gates and the wall by being sprinkled.