John Gill Commentary 2 Chronicles 24:4

"And it came to pass after this, that Joash was minded to restore the house of Jehovah." — 2 Chronicles 24:4 (ASV)

And it came to pass after this
After his marriage, when he was about twenty or twenty one years of age, perhaps:

that Joash was minded to repair the house of the Lord ;
which in some places might be fallen to decay, having been built one hundred and fifty years or more, and in others defaced by Athaliah, and needed ornamenting, see (2 Kings 12:4) .