In the Church of Virginia on May 10, 1789, Washington stated:
If I could have entertained the slightest apprehension that the Constitution framed by the Convention, where I had the honor to preside, might possibly endanger the religious rights of any ecclesiastical Society, certainly I would never have placed my signature to it; I beg you will be persuaded that no one would be more zealous than myself to establish effectual barriers against… every species of religious persecution.

George Washington issued a National Day of Thanksgiving Proclamation on October 3, 1789:
Whereas it is the duty of all nations to acknowledge the providence of Almighty God, to obey His will, to be grateful for his benefits, and humbly to implore His protection and favor… that we then may all unite unto him our sincere and humble thanks for His kind care and protection of the people of this country… And also that we may then unite in most humbly offering our prayers and supplications to the great Lord and Ruler of Nations, and beseech Him to pardon our national and other transgressions… and to bless them with good government, peace, and concord, to promote the knowledge and practice of the true religion and virtue, and the increase of science.

On October 9, 1789, President George Washington wrote to the Synod of the Dutch Reformed Churches in North America:
While just government protects all in their religious rights, true religion affords to government its surest support.

On January 1, 1795, President George Washington issued another National Thanksgiving Proclamation:
It is in an especial manner our duty as a people, with devout reverence and affectionate gratitude, to acknowledge our many and great obligations to Almighty God, and to implore Him to continue and confirm the blessings we experienced.

George Washington articulated his understanding of what will keep America great:
It is impossible to rightly govern the world without God and the Bible.
It is impossible to account for the creation of the universe, without the agency of a Supreme Being. It is impossible to govern the universe without the aid of a Supreme Being. It is impossible to reason without arriving at a Supreme Being. Religion is as necessary to reason, as reason is to religion. The one cannot exist without the other. A reasoning being would lose his reason, in attempting to account for the great phenomena of nature, had he not a Supreme Being to refer to.

President George Washington, in his Farewell Speech on September 19, 1796, said:
The name of AMERICAN, which belongs to you, in your national capacity, must always exalt the just pride of Patriotism, more than any appellation derived from local discriminations. With slight shades of difference, you have the same Religion, Manners, Habits, and political Principles…
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 prosperity, for reputation, for life, if the sense of religious obligation desert the oaths, which are the instruments of investigation in the 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.

Tis substantially true, that virtue or morality is a necessary spring of popular government.

Who that is a sincere friend to it, can look with indifference upon attempts to shake the foundation of the fabric?

Religion and Morality enjoin this conduct; and can it be that good policy does not equally enjoin it?… Can it be that Providence has not connected the permanent felicity of a Nation with its virtue?

quotes from: George Washington, Founding Father, General in Command of the Continental Army, President of the Constitutional Convention, First President of the United States, Father of the Nation

On July 9, 1776, the Continental Congress authorized the Continental Army to provide chaplains for their troops. On that same day, Washington issued the general order to his troops, stating:

The General hopes and trusts that every officer and man, will endeavor so to live, and act, as becomes a Christian Soldier defending the dearest Rights and Liberties of his country.

On May 2, 1778, General George Washington issued these orders to his troops at Valley Forge:

While we are zealously performing the duties of good citizens and soldiers, we certainly ought not to be inattentive to the higher duties of religion. To the distinguished character of Patriot, it should be our highest Glory to laud the more distinguished Character of Christian. The signal instances of Providential goodness which we have experienced and which have now almost crowned our labors with complete success demand from us in a peculiar manner the warmest returns of gratitude and piety to the Supreme Author of all good.

On August 20, 1778, General George Washington wrote to his friend, Brigadier-General Thomas Nelson in Virginia:

The hand of Providence has been so conspicuous in all this (the course of the war) that he must be worse than an infidel that lacks faith, and more wicked that has not gratitude to acknowledge his obligations; but it will be time enough for me to turn Preacher when my present appointment ceases.

On May 12, 1779, General George Washington was visited at his military encampment by some chiefs of the Delaware Indian tribe. They had brought three youths to be trained in the American schools. Washington assured them, commenting:

Congress will look upon them as their own Children… You do well to wish to learn our arts and ways of life, and above all, the religion of Jesus Christ. These will make you a greater and happier people than you are. Congress will do everything they can to assist you in this wise intention.

On June 8, 1783, at the conclusion of the Revolutionary War, General George Washington sent a farewell circular letter from his headquarters in Newburgh, New York, to all thirteen Governors of the newly freed states. He stated:

I now make it my earnest prayer that God would have you, and the State over which you preside, in his holy protection… that he would most graciously be pleased to dispose us all to do justice, to love mercy, and to demean ourselves with that charity, humility, and pacific temper of mind, which were the characteristics of the Divine Author of our blessed religion, and without an humble imitation of whose example in these things, we can never hope to be a happy nation.

Washington’s Prayer for the United States of America appears on a plaque in St. Paul’s Chapel in New York City as well as at Pohick Church, Fairfax County, Virginia, where Washington was a vestryman from 1762 to 1784:
Almighty God; We make our earnest prayer that Thou wilt keep the United States in Thy Holy protection; and Thou wilt incline the hearts of the Citizens to cultivate a spirit of subordination and obedience to Government; and entertain a brotherly affection and love for one another and for their fellow Citizens of the United States at large, and particularly for their brethren who have served in the Field.

And finally that Thou wilt most graciously be pleased to dispose us all to do justice, to love mercy, and to demean ourselves with that Charity, humility, and pacific temper of mind which were the Characteristics of the Divine Author of our blessed Religion, and without a humble imitation of whose example in these things we can never hope to be a happy nation. Grant our supplication, we beseech Thee, through Jesus Christ our Lord. Amen.

A week prior to the Inauguration, April 23, 1789, the schedule of events for that special day was published in the newspaper, Daily Advertiser:

On the morning of the day on which our illustrious President will be invested with his office, the bells will ring at nine o’clock, when the people may go up and in a solemn manner commit the new Government, with its important train of consequences, to the holy protection and blessings of the Most High. An early hour is prudently fixed for this peculiar act of devotion, and it is designed wholly for prayer.

In his Inaugural Speech to Both Houses of Congress, April 30, 1789, George Washington proclaimed:
…in this first official act, my fervent supplications to that Almighty Being who rules over the universe, who presides in the councils of nations and whose providential aids can supply every human defect, that His benediction may consecrate to the liberties and happiness of the people of the United States…

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 finally, staked of the experiment…

In addressing the General Committee representing the United Baptist
America’s God and Country by William J. Federer