“Since we ought to be no less persuaded that the propitious smiles of Heaven, can never be expected on a nation that disregards the eternal rules of order and right, which Heaven itself has ordained: And since the preservation of the sacred fire of liberty, and the destiny of the Republican model of Government, are justly considered as deeply, perhaps as finally staked, on the experiment entrusted to the hands of the American people.”.... George Washington—Inaugural speech excerpt...
http://www.archives.gov/exhibits/american_originals/inaugtxt.html
"Of all the dispositions and habits which lead to political prosperity, religion and morality are indispensable supports. In vain would that man claim the tribute of patriotism, who should labor to subvert these great pillars of human happiness, these firmest props of the duties of men and citizens. The mere politician, equally with the pious man, ought to respect and to cherish them. A volume could not trace all their connections with private and public felicity. Let it simply be asked: Where is the security for property, for reputation, for life, if the sense of religious obligation desert the oaths which are the instruments of investigation in courts of justice ? And let us with caution indulge the supposition that morality can be maintained without religion. Whatever may be conceded to the influence of refined education on minds of peculiar structure, reason and experience both forbid us to expect that national morality can prevail in exclusion of religious principle."
From Washington's Farewell.