Charles Ellicott Commentary 2 Chronicles 30:12

"Also upon Judah came the hand of God to give them one heart, to do the commandment of the king and of the princes by the word of Jehovah." — 2 Chronicles 30:12 (ASV)

Also in Judah ... was. —Rather, Moreover upon Judah was the hand of God: a phrase here used of a Divine influence for good. (Compare to Ezra 8:22.) Elsewhere the phrase has the sense of judicial visitation; for example, Exodus 9:3.

The commandment ... by the word of the Lord. —Compare to a similar phrase, 2 Chronicles 29:15. The royal command was inspired by the word of the Lord through a prophet.