What does 1 Chronicles 15:12 mean?

He told them, 'You are the heads of the Levite families. You and your relatives need to make yourselves ritually clean, so you can bring up the chest of the Lord, the God of Israel, to the place I’ve prepared.' 1 Chronicles 15:12 - Modern Text Bible

(David stresses the need for spiritual preparation, not just physical action. The leaders must be clean before handling the Ark.)