Charles Finney emphasizes the significance of national fasting as a means of public repentance and acknowledgment of national sins. He outlines the essential elements of an acceptable fast, including genuine sorrow, confession, and a commitment to reform. Finney argues that human governments are divinely instituted and that citizens, especially Christians, have a duty to engage in national fasts to seek God's mercy and avert judgment. He highlights various national sins, such as the treatment of Native Americans and the institution of slavery, that necessitate collective humility and prayer. The sermon calls for a sincere commitment to reform alongside fasting, warning against the hypocrisy of seeking God's favor without genuine change.