Why is personal repentance, in your heart, not enough now that the whole people have fallen away from God?

Going to God personally, in your heart, is not enough. It also needs to become evident on the outside that the people as a whole are seeking help from God in this need. A solemn assembly must be organized. As a sign of sorrow, the people are to abstain from food and drink (fasting). No one may be excused from this. It needs to happen in the place where God lives, in the house of God: the temple. In this way the people show that they are seeking their help from God and expect deliverance from him. Priests and elders—the spiritual and civil leaders—are to lead the people in this. Joel urges the proper functioning of the worship service established by God. God has established a regular worship service, so take it seriously and give expression to it. Serve God with your heart, but also according to his concrete rules.