פירוש על דברי הימים א 23:28

For their station was alongside the sons of Aaron, etc. This resembles (Num. 18:2): “... and they shall join with you and minister to you.”

and over the purity of all sacred things so that if the House and its vessels become unclean, they will be appointed to purify it, for so we find with Hezekiah, as it is written (below II Chron. 29:16): “And the Levites accepted to take out to the Kidron Valley outside,” and it is written (ibid. verse 17): “And they commenced on the first of the first month to sanctify, etc.”