“As we maintain the vigil of peace, we must remember that justice is a vigil, too — a vigil we must keep in our own streets and schools and among the lives of all our people — so that those who died here on their native soil shall not have died in vain.”

Source: The Sweet Far Thing

1990s
Context: We have depended on government for so much for so long that we as people have become less vigilant of our liberties. As long as the government provides largesse for the majority, the special interest lobbyists will succeed in continuing the redistribution of welfare programs that occupies most of Congress's legislative time.

Speech in the House of Representatives, September 17, 1997

As quoted in "Donald Trump claims parts of London are 'so radicalised' police officers are 'afraid for their lives'" http://www.independent.co.uk/news/people/donald-trump-claims-parts-of-london-are-so-radicalised-police-officers-are-afraid-for-their-lives-a6765026.html by Rose Troup Buchanan, The Independent (8 December 2015); also in "'Trump's not wrong – we can't wear uniform in our OWN cars': Five police officers claim Donald Trump is RIGHT about parts of London being so 'radicalised' they are no-go areas" http://www.dailymail.co.uk/news/article-3352406/Scotland-Yard-mocks-Trump-s-claims-London-police-terrified-Muslim-areas-officers-claim-tycoon-RIGHT.html by Martin Robinson, Daily Mail Online (9 December 2015)
2010s, 2015

2013, "Let Freedom Ring" Ceremony (August 2013)
Context: To dismiss the magnitude of this progress -- to suggest, as some sometimes do, that little has changed -- that dishonors the courage and the sacrifice of those who paid the price to march in those years. Medgar Evers, James Chaney, Andrew Goodman, Michael Schwerner, Martin Luther King Jr. -- they did not die in vain. Their victory was great. But we would dishonor those heroes as well to suggest that the work of this nation is somehow complete. The arc of the moral universe may bend towards justice, but it doesn’t bend on its own. To secure the gains this country has made requires constant vigilance, not complacency. Whether by challenging those who erect new barriers to the vote, or ensuring that the scales of justice work equally for all, and the criminal justice system is not simply a pipeline from underfunded schools to overcrowded jails, it requires vigilance. And we'll suffer the occasional setback. But we will win these fights. This country has changed too much. People of goodwill, regardless of party, are too plentiful for those with ill will to change history’s currents.

Senate speech, 30 May 2003 (excerpts)

Farewell Address, (4 March 1837), recalling what, by then, had reached the status of a proverb.
1830s

Presidency (1977–1981), Inaugural Address (1977)
Context: The world itself is now dominated by a new spirit. Peoples more numerous and more politically aware are craving and now demanding their place in the sun – not just for the benefit of their own physical condition, but for basic human rights.
The passion for freedom is on the rise. Tapping this new spirit, there can be no nobler nor more ambitious task for America to undertake on this day of a new beginning than to help shape a just and peaceful world that is truly humane.
We are a strong nation, and we will maintain strength so sufficient that it need not be proven in combat – a quiet strength based not merely on the size of an arsenal, but on the nobility of ideas.
We will be ever vigilant and never vulnerable, and we will fight our wars against poverty, ignorance, and injustice – for those are the enemies against which our forces can be honorably marshaled.
We are a purely idealistic Nation, but let no one confuse our idealism with weakness.
Because we are free we can never be indifferent to the fate of freedom elsewhere. Our moral sense dictates a clearcut preference for these societies which share with us an abiding respect for individual human rights. We do not seek to intimidate, but it is clear that a world which others can dominate with impunity would be inhospitable to decency and a threat to the well-being of all people.

Address to the United Nations (1963)
Context: The Charter of the United Nations expresses the noblest aspirations of man: abjugation of force in the settlement of disputes between states; the assurance of human rights and fundamental freedoms for all without distinction as to race, sex, language or religion; the safeguarding of international peace and security.
But these, too, as were the phrases of the Covenant, are only words; their value depends wholly on our will to observe and honour them and give them content and meaning. The preservation of peace and the guaranteeing of man's basic freedoms and rights require courage and eternal vigilance: courage to speak and act — and if necessary, to suffer and die — for truth and justice; eternal vigilance, that the least transgression of international morality shall not go undetected and unremedied.
These lessons must be learned anew by each succeeding generation, and that generation is fortunate indeed which learns from other than its own bitter experience. This Organization and each of its members bear a crushing and awesome responsibility: to absorb the wisdom of history and to apply it to the problems of the present, in order that future generations may be born, and live, and die, in peace.

Source: The Chocolate War (1974), p. 27