Notes on the Bible, by Albert Barnes, [1834], at sacred-texts.com
This chapter is entirely additional to Kings, and of great interest. It deals with three matters only,
(1) The rebuke addressed to Jehoshaphat by the prophet Jehu Ch2 19:1-3,
(2) Jehoshaphat's religious reformation Ch2 19:4, and
(3) his reform of the judicial system Ch2 19:5-11.
Jehoshaphat ... returned to his house in peace - With the battle of Ramoth-Gilead, and the death of Ahab, the war came to an end. The combined attack of the two kings having failed, their troops had been withdrawn, and the enterprise in which they had joined relinquished. The Syrians, satisfied with their victory, did not press on the retreating foe, or carry the war into their enemies' country.
Jehu ... went out to meet him - Compare Ch2 15:2. The monarch was therefore rebuked at the earliest possible moment, and in the most effective way, as he was entering his capital at the head of his returning army. Jehu, 35 years previously, had worked in the northern kingdom, and prophesied against Baasha Kg1 16:1-7, but had now come to Jerusalem, as prophet and historian (compare Ch2 20:34).
Shouldest thou help ... - As a matter of mere human policy, the conduct of Jehoshaphat in joining Ahab against the Syrians was not only justifiable but wise and prudent. And the reasonings upon which such a policy was founded would have been unexceptionable but for one circumstance. Ahab was an idolater, and had introduced into his kingdom a false religion of a new and most degraded type. This should have led Jehoshaphat to reject his alliance. Military success could only come from the blessing and protection of Yahweh, which such an alliance, if persisted in, was sure to forfeit.
Jehoshaphat, while declining to renounce the alliance with Israel (compare the Kg2 3:7 note), was careful to show that he had no sympathy with idolatry, and was determined to keep his people, so far as he possibly could, free from it. He therefore personally set about a second reformation, passing through the whole land, from the extreme south to the extreme north Ch2 13:19.
What exact change Jehoshaphat made in the judicial system of Judah Deu 16:18; Ch1 23:4, it is impossible to determine. Probably he found corruption widely spread Ch2 19:7, and the magistrates in some places tainted with the prevailing idolatry. He therefore made a fresh appointment of judges throughout the whole country; concentrating judicial authority in the hands of a few, or creating superior courts in the chief towns ("fenced cities"), with a right of appeal to such courts from the village judge.
The "fathers of Israel" are the heads of families; the chief of the fathers" are the great patriarchal chiefs, the admitted heads of great houses or clans. They were now admitted to share in the judicial office which seems in David's time to have been confined to the Levites Ch1 23:4.
For the judgment of the Lord, and for controversies - By the former are meant disputed cases concerning the performance of religious obligations. In "controversies" are included all the ordinary causes, whether criminal or civil.
When they returned to Jerusalem - Rather, "and they returned to Jerusalem," a clause which if detached from the previous words and attached to Ch2 19:9, gives a satisfactory sense.
The Jews who "dwelt in the cities," if dissatisfied with the decision given by the provincial judges, might therefore remove the cause to Jerusalem, as to a court of appeal.
In religious causes, Amariah, the high priest, was to preside over the court; in civil or criminal causes, Zebadiah was to be president. And to Levites, other than the judges, he assigned the subordinate offices about the court.