From: Bible.com - Discover the Bible and Liberty in History: Day 1 • Devotional

John Witherspoon, the only clergyman to sign the Declaration of Independence, retired from the Continental Congress in 1782. One of his last acts in Congress was leading a committee to draft a proclamation of a day of thanksgiving for the end of the Revolutionary War. A month later, on the assigned day, he preached a lengthy sermon. His text was Psalm 3:8, and he compared the war with the setting of the psalm (during David’s conflict with Absalom) as a lingering conflict with victory in sight. Given the clear hand of Providence in the American victory against all odds (he quoted Genesis 18:14 and Psalm 34:19), he argued, the grateful response of clergy, families, and all those “vested with civil authority” should be “with much care, to promote religion and good morals among all under their government.” Then he explained why.

“I hope none here will deny, that the manners of the people, in general, are of the utmost moment to the stability of any civil society. When the body of a people is altogether corrupt in its manners, the government is ripe for dissolution. Good laws may hold the rotten bark some longer together, but in a little time, all laws must give way to the tide of popular opinion, and be laid prostrate under universal practice.…"

“[I]n free states, where the body of the people have the supreme power properly in their own hands, and must be ultimately resorted to on all great matters, if there be a general corruption of manners, there can be nothing but confusion. So true is this, that civil liberty cannot be preserved long without virtue. A monarchy may subsist for ages, and be better or worse under a good or bad prince, but a republic once equally poised, must either preserve its virtue or lose its liberty, and by some tumultuous revolution, either return to its first principles or assume a more unhappy form.…"

“And in our families let us do the best by religious instruction, to sow the seeds which may bear fruit in the next generation. We are one of the bodies of confederated States. For many reasons, I shall avoid making any comparisons at present, but may venture to predict, that whatsoever State among us shall continue to make piety and virtue the standard of public honor, will enjoy the greatest inward peace, the greatest national happiness, and in every outward conflict will discover the greatest constitutional strength.”