Joel was written during the locust plague, a time of great distress for the people. The prophet sees in the devastation of the locusts an indication of the coming of the day of the Lord. Therefore all must repent with fasting and mourning. With repentance, however, there is a promise of relief and God’s blessing for Israel.

Joel 2

2:28 And it shall come to pass afterward, that I will pour out my spirit upon all flesh; and your sons and your daughters shall prophesy, your old men shall dream dreams, your young men shall see visions: