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 1

1:13 Gird yourselves, and lament, ye priests: howl, ye ministers of the altar: come, lie all night in sackcloth, ye ministers of my God: for the meat offering and the drink offering is withholden from the house of your God.