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

3:6 The children also of Judah and the children of Jerusalem have ye sold unto the Grecians, that ye might remove them far from their border.