the whole assembly made a covenant with the king in the house of God. “Behold, the king’s son!” said Jehoiada. “He must reign, just as the LORD promised concerning the descendants of David.
We may well imagine the bad posture of affairs in Jerusalem during Athaliah's six years' usurpation, and may wonder that God permitted it and his people bore it so long; but after such a dark and tedious night the returning day in this revolution was the brighter and the more welcome.
Commenting on 2 Chronicles 23:1-11
After Joash had been kept in hiding for six years, the high priest Jehoiada came to the resolution to make an end of the tyranny of Athaliah, and to raise the young prince to the throne. The carrying out of this resolution is narrated in 2 Chron 23, and thereafter in 2 Chron 24. All that is important as to the reign of Joash is communicated.
Commenting on 2 Chronicles 23:1-3