“It was a creed written into the founding documents that declared the destiny of a nation.”

2017, Farewell Address (January 2017)

L'exemple souvent n'est qu'un miroir trompeur;
Et l'ordre du destin qui gêne nos pensées
N'est pas toujours écrit dans les choses passées.
Auguste, act II, scene i.
Cinna (1641)

All tyrants, past, present and future, are powerless to bury the truths in these declarations, no matter how extensive their legions, how vast their power and how malignant their evil.
1960s, Emancipation Proclamation Centennial Address (1962)

2013, Second Inaugural Address (January 2013)
Context: We, the people, still believe that our obligations as Americans are not just to ourselves, but to all posterity.  We will respond to the threat of climate change, knowing that the failure to do so would betray our children and future generations. Some may still deny the overwhelming judgment of science, but none can avoid the devastating impact of raging fires and crippling drought and more powerful storms. The path towards sustainable energy sources will be long and sometimes difficult. But America cannot resist this transition, we must lead it. We cannot cede to other nations the technology that will power new jobs and new industries, we must claim its promise. That’s how we will maintain our economic vitality and our national treasure -- our forests and waterways, our crop lands and snow-capped peaks. That is how we will preserve our planet, commanded to our care by God. That’s what will lend meaning to the creed our fathers once declared.

Centennial Oration (4 July 1876) http://www.infidels.org/library/historical/robert_ingersoll/centennial_oration.html
Context: p>One hundred years ago, our fathers retired the gods from politics.The Declaration of Independence is the grandest, the bravest, and the profoundest political document that was ever signed by the representatives of a people. It is the embodiment of physical and moral courage and of political wisdom.</p

Iowa Caucus Victory Speech, Delivered at the Iowa Democratic caucus on 3 January 2008 http://www.youtube.com/watch?v=cNZaq-YKCnE
2008

Address in Washington D.C. (22 March 1978) http://www.jewishvirtuallibrary.org/jsource/US-Israel/Carter_Begin5.html

Memorial Day address, Arlington National Cemetery (31 May 1976) http://www.presidency.ucsb.edu/ws/index.php?pid=6071
1970s
Context: The founding of our Nation was more than a political event; it was an act of faith, a promise to Americans and to the entire world. The Declaration of Independence declared that people can govern themselves, that they can live in freedom with equal rights, that they can respect the rights of others.
In the two centuries that have passed since 1776, millions upon millions of Americans have worked and taken up arms when necessary to make that dream a reality. We can be extremely proud of what they have accomplished. Today, we are the world's oldest republic. We are at peace. Our Nation and our way of life endure. We are free.

Preface to A Way Out : A One-act Play (1929)
General sources
Context: Everything written is as good as it is dramatic. It need not declare itself in form, but it is drama or nothing. A least lyric alone may have a hard time, but it can make a beginning, and lyric will be piled on lyric till all are easily heard as sung or spoken by a person in a scene — in character, in a setting. By whom, where and when is the question.