Albert Barnes Commentary 2 Chronicles 29:15

"And they gathered their brethren, and sanctified themselves, and went in, according to the commandment of the king by the words of Jehovah, to cleanse the house of Jehovah." — 2 Chronicles 29:15 (ASV)

By the words of the Lord — Rather, as suggested in the margin, “According to the commandment of the king in the business (or matters) of the Lord.”