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 3

3:4 Yea, and what have ye to do with me, O Tyre, and Zidon, and all the coasts of Palestine? will ye render me a recompense? and if ye recompense me, swiftly and speedily will I return your recompense upon your own head;