Jehoshaphat feared; partly from human frailty, and partly from the remembrance of his own guilt, and the wrath of God denounced against him for it, 2Ch_19:2.
Set himself to seek the Lord: the phrase notes his settled resolution, seriousness, and earnestness in it, and the preparing and fixing his heart for it.
Proclaimed a fast; partly in token of his humiliation and penitence for his sins, and partly to make himself and his people more fervent in their prayers.