What does 2 Chronicles 30:15 mean?

Then they killed the Passover lamb on the fourteenth day of the second month. The priests and Levites felt ashamed, so they purified themselves and brought burnt offerings to the Lord’s temple. 2 Chronicles 30:15 - Modern Text Bible

(The Passover is celebrated a month late, and the priests and Levites, feeling convicted, make sure they’re ritually clean before serving.)