Albert Barnes Commentary 2 Kings 12:4

"And Jehoash said to the priests, All the money of the hallowed things that is brought into the house of Jehovah, in current money, the money of the persons for whom each man is rated, and all the money that it cometh into any man`s heart to bring into the house of Jehovah," — 2 Kings 12:4 (ASV)

It is remarkable that the first movement toward restoring the fabric of the temple should have come not from Jehoiada, but from Jehoash (Compare to 2 Chronicles 24:4). It seems Jehoiada had allowed the damage done in Athaliah’s time to remain unrepaired during the whole term of his government.

The money of every one... Three kinds of sacred money are distinguished here:

1. The half-shekel required by the Law (Exodus 30:13) to be paid by everyone over twenty years of age when they were counted in the census.
2. The money to be paid by those who had devoted themselves, or people belonging to them, by a vow to Yahweh, which was a variable sum dependent on age, sex, and property (Leviticus 27:2–8).
3. The money offered as free-will offerings.