Adam Clarke on 2 Chronicles 30:22

Spake comfortably unto all the Levites - On such occasions the priests and Levites had great fatigue, and suffered many privations; and therefore had need of that encouragement which this prudent and pious king gave. It is a fine and expressive character given of these men, "They taught the good knowledge of God to the people." This is the great work, or should be so, of every Christian minister. They should convey that knowledge of God to the people by which they may be saved; that is, the good knowledge of the Lord.