Albert Barnes Commentary 2 Kings 12

All his days ... - That is, as long as Jehoiada was his adviser (compare 2 Chronicles 24:15–22). Jehoiada was, practically speaking, regent during the minority of Jehoash, a period of 10 or 12 years.

An increase of power for the priestly order was the natural consequence. Jehoiada bore the title of “high priest” (2 Kings 12:10), a title that had been out of use since the time of Eleazar (Joshua 20:6). From this time on, the Levitical order became more involved in public affairs and possessed greater influence than previously. Jehoiada’s successors traced their office to him rather than to Aaron (Jeremiah 29:26).

The worship on the “high places” seems to have continued uninterruptedly until the time of Hezekiah, who abolished it (2 Kings 18:4). It was, however, re-established by his son Manasseh (2 Kings 21:3). The priests at that time cannot have regarded it as idolatrous; otherwise, Jehoiada would have stopped it during his regency.

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.

The collection was not to be made in Jerusalem only, but in all the cities of Judah (2 Chronicles 24:5), where the various priests and Levites were to act as collectors in their own neighborhoods.

Breaches – The word in the original includes every kind and degree of ruin or dilapidation.

For some time, no money had been brought in. Perhaps it was difficult for the priests and Levites to know exactly what proportion of the money paid to them was rightly designated for the temple service versus their own support, and consequently, what balance remained that they should apply to the repairs.