The book of Joel foretells the last days and the judgment of the Lord upon the nations. A plague of locusts invaded Judah, presaging the coming of the Lord on judgment day. After an assembly of the people was gathered and the priests prayed for deliverance, the Lord heard their prayer and promised to send peace and prosperity on Judah instead. Still, the Lord's vengeance will be meted out on Judah's faithless neighbors as God sounds not only jealous of Judah's affection, but angry over the suffering they have borne from their neighbors.
There's never a time I consider God's justice and mercy that my head doesn't start spinning after a while. It's a good thing I don't have to figure it out. It's well that we remember "God is God, and I am not."
Our response is fairly simple: confess our sins and depend on the mercy and justice of God; confess our sins and receive Jesus' Body and Blood. I'm not sure Tissot's Joel would be too merciful a fellow, just looking at him. I'll take Jesus, thank you.
Joel by James Tissot.