General fasts had been previously observed by the Israelites (e. g. Judges 20:26; 1 Samuel 7:6); but we do not hear of any fast having been "proclaimed" by authority before this.

Jehoshaphat feared - He found that he could not possibly stand against such a numerous army, and therefore could not expect to be delivered except by the strong arm of God. To get this assistance, it was necessary to seek it; and to get such extraordinary help, they should seek it in an extraordinary way; hence he proclaimed a universal fast, and all the people came up to Jerusalem to seek the Lord.

And Jehoshaphat feared,.... Exceedingly, as the Targum adds, not merely because of the number of his enemies, for he had forces enough to go forth against them, see 2 Chronicles 17:14, but chiefly because the Lord had told him that wrath was upon him from him, 2 Chronicles 19:2 and he might fear that this was the time for the execution of it:

and set himself to seek the Lord; by prayer and supplication, with all seriousness, fervour, and constancy:

and proclaimed a fast throughout all Judah; a day of humiliation and mourning for sin before the Lord; when they were ordered to abstain from bodily food and labour, that they might be fit and more at leisure for spiritual exercises.

This report filled Jehoshaphat with fear, and he resolved to seek help of the Lord. ??????? נתן equals שׂוּם , cf. 2 Kings 12:18; Jeremiah 42:15, to direct the face to anything, i.e., to purpose something, come to a determination. He proclaimed a fast in all Judah, that the people might bow themselves before God, and supplicate His help, as was wont to be done in great misfortunes; cf. Judges 20:26; 1 Samuel 7:6; Isaiah 2:15. In consequence of the royal appeal, Judah came together to seek of the Lord, i.e., to pray for help, by fasting and prayer in the temple; and it was not only the inhabitants of Jerusalem who thus assembled, for they came out of all the cities of the kingdom. מיהוה בּקּשׁ, to seek of the Lord, sc. help, is expressed in the last clause by את־יהוה בּקּשׁ to seek the Lord.

And Jehoshaphat feared, and set himself {c} to seek the LORD, and proclaimed a fast throughout all Judah.

(c) This declares what the fear of the godly is, which is the prick to stir them to prayer and to depend on the Lord, while it moves the wicked either to seek after worldly means and policies or else to fall into despair.

himself: Heb. his face

3, 4. Jehoshaphat . proclaimed a fast throughout all Judah-Alarmed by the intelligence and conscious of his total inability to repel this host of invaders, Jehoshaphat felt his only refuge was at the horns of the altar. He resolved to employ the aid of his God, and, in conformity with this resolution, he summoned all his subjects to observe a solemn fast at the sanctuary. It was customary with the Hebrew kings to proclaim fasts in perilous circumstances, either in a city, a district, or throughout the entire kingdom, according to the greatness of the emergency. On this occasion, it was a universal fast, which extended to infants (2Ch 20:13; see also Joe 2:15, 16; Jon 3:7).

20:1-13 In all dangers, public or personal, our first business should be to seek help from God. Hence the advantage of days for national fasting and prayer. From the first to the last of our seeking the Lord, we must approach him with humiliation for our sins, trusting only in his mercy and power. Jehoshaphat acknowledges the sovereign dominion of the Divine Providence. Lord, exert it on our behalf. Whom should we seek to, whom should we trust to for relief, but the God we have chosen and served. Those that use what they have for God, may comfortably hope he will secure it to them. Every true believer is a son of Abraham, a friend of God; with such the everlasting covenant is established, to such every promise belongs. We are assured of God's love, by his dwelling in human nature in the person of the Saviour. Jehoshaphat mentions the temple, as a token of God's favourable presence. He pleads the injustice of his enemies. We may well appeal to God against those that render us evil for good. Though he had a great army, he said, We have no might without thee; we rely upon thee.