Joel is a short prophetic book which evocatively describes the ravages of a “locust army”. Locust swarms represent a massive catastrophe for any agrarian society, and the prophet Joel uses this image to represent forthcoming judgement, on “the day of the LORD”.
The language is poetic, the text is difficult to date exactly, little is known about the author…It is no surprise that the exact interpretation of this book is the subject of some scholarly debate. For more on the interpretative challenges of Joel, the ESV study bible offers a more thorough overview here.
The prophetic ideas of judgement and salvation are central, and Joel expresses the idea that God will judge, but he will also protect and deliver His people in the midst of devastation and catastrophe.
How does a nation survive if the Holy God is in their midst? Where Holiness is, there is judgement and wrath at sin. Joel uses powerful pictures to express the gravity and extent of the problems that sin creates for us.
But because God is one who keeps his covenants, He offers grace and hope for the repentant: He will be a “stronghold” and a “refuge” for His people. (3:16-17)