John Gill Commentary 2 Chronicles 24:20

"And the Spirit of God came upon Zechariah the son of Jehoiada the priest; and he stood above the people, and said unto them, Thus saith God, Why transgress ye the commandments of Jehovah, so that ye cannot prosper? because ye have forsaken Jehovah, he hath also forsaken you." — 2 Chronicles 24:20 (ASV)

And the Spirit of the Lord came upon Zechariah the son of
Jehoiada the priest
The spirit of prophecy, as the Targum; he was moved and influenced by it to speak what is after related:

which stood above the people ;
in a desk, or sort of pulpit, in which the priests stood when they taught the people, that they might be the better heard, like that which Ezra used, (Nehemiah 8:4)

and said unto them, thus saith God ;
being moved and directed by his Spirit, he spoke in his name:

why transgress you the command of the Lord, that you cannot prosper ?
by committing idolatry, than which nothing could more hinder prosperity, both in things spiritual and temporal, in soul and body:

because you have forsaken the Lord, he has also forsaken you ;
because they had forsaken the worship of God, as the Targum, God had forsaken them, and was about to give them up into the hand of their enemies.