Hebrew Yoel, "Yahweh is God." Date uncertain — estimates range from the ninth century BC to the postexilic period; internal evidence is consistent with either. Joel's ministry opens with a devastating locust plague that has stripped Judah bare — no grain, no wine, no oil. Joel interprets the locusts as a harbinger of a greater "Day of the LORD" to come, calls for national fasting and repentance, and promises that if Israel returns, God will restore the years the locusts have eaten. The book builds to a magnificent climax in chapter 2.
Joel's signature passage is the prophecy quoted by Peter on the day of Pentecost (Acts 2:17-21): "And it shall come to pass afterward, that I will pour out my Spirit on all flesh; your sons and your daughters shall prophesy, your old men shall dream dreams, and your young men shall see visions. Even on the male and female servants in those days I will pour out my Spirit" (Joel 2:28-29). This universalized promise — the Spirit poured on all flesh, not just priests and prophets — is the Pentecostal constitution of the New Covenant Church. Peter declares it fulfilled: "This is what was uttered through the prophet Joel." Joel's other great gift is the call to repentance in 2:12-13: "'Yet even now,' declares the LORD, 'return to me with all your heart, with fasting, with weeping, and with mourning; and rend your hearts and not your garments.'" The emphasis on the inward reality rather than external ritual echoes throughout Scripture. Joel's final vision (chapter 3) shows the nations gathered for judgment in the Valley of Jehoshaphat (meaning "Yahweh judges") and concludes with Yahweh dwelling in Zion with His people forever.