How do we know that God's call to preach is effective?

The effectiveness of God's call to preach is demonstrated through the repentance of the Ninevites in Jonah's time and the change of lives that follows the proclamation of the gospel. Preaching is not merely an intellectual exercise; it is divinely empowered to change hearts and lives. God often uses the proclamation of truth to awaken spiritual awareness and bring about genuine repentance. Responding to the call to preach, when done faithfully, leads to tangible results as seen in instances throughout Scripture where entire communities turned to God.