2 Chronicles 20:3

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

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 implore the aid of his God, and, in conformity with this resolution, summoned his whole 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 (2 Chronicles 20:13: see also Joel 2:15; Jonah 3:7).