Joel, prophetic book of the Bible. It is a collection of the oracles of an otherwise unknown prophet, dated variously from the 9th to the 3d cent. B.C., though a date in c.400 B.C. is likely. A locust plague gives the prophet the prextext for summoning the whole nation to repentance; the people, on repentance, will be rewarded with present as well as future blessings, this being a prophecy concerning the Day of the Lord—a day on which the faithful will be vindicated while the Gentile enemies of the people of God will be overthrown. H. W. Wolff, Joel and Amos (1977); W. S. Prinsloo, The Theology of the Book of Joel (1985).