Joel shows the people that it is God who brings his judgments on the people. Then he urges them to go to this God to cry out to the hand that smites you.
That is part of your faith in God, the only God. You can never find help anywhere else but with God. Your logical reaction might be to get angry with the person who is bringing all this disaster upon you. However, the prophet shows that even when he punishes and turns against you, God is the only helper. You know God, don’t you? You know that he never punishes unjustly, right? Therefore, when God gets angry and comes with judgments, you have to look at yourself. This is what Joel calls the leaders and the people to do. As a prophet, he opens the eyes to what is going on in his days. In the same way he also points the way out of the difficulties. Joel does this based on the words that God spoke to him (Joel 1:1). This shows God’s compassion for his people. Despite their sins, he loves them and wants to deliver them from his (righteous) punishments.
14 Consecrate a fast; call a solemn assembly. Gather the elders and all the inhabitants of the land to the house of the LORD your God, and cry out to the LORD.