“We cannot defer this responsibility to posterity. Time will not wait.”

Alençon, Act III, scene ii.
Henry VI, Part 1 (1592)

First inaugural address (January 20, 1993), Washington, D.C.
1990s

Senator Barack Obama’s speech to supporters after the Feb. 5 2018 nominating contests, as provided by Federal News Service and released in the New York Times (5 February 2008) https://www.nytimes.com/2008/02/05/us/politics/05text-obama.html
2008

Quoted on the website of the IMT http://www.marxist.com/historic-32nd-congress-of-pakistani-imt-1.htm: Statement to the 32nd congress of Pakistani Marxists
Statement to 32nd Congress of Pakistani Marxists, March 2013
Context: First of all I’d like to thank The Struggle and the IMT for giving me a chance to speak last year at their Summer Marxist School in Swat and also for introducing me to Marxism and Socialism. I just want to say that in terms of education, as well as other problems in Pakistan, it is high time that we did something to tackle them ourselves. It’s important to take the initiative. We cannot wait around for any one else to come and do it. Why are we waiting for someone else to come and fix things? Why aren’t we doing it ourselves? I would like to send my heartfelt greetings to the congress. I am convinced Socialism is the only answer and I urge all comrades to take this struggle to a victorious conclusion. Only this will free us from the chains of bigotry and exploitation.

Ми чекамо Христа, а не боље време.
Prayerful songs http://www.svetosavlje.org/biblioteka/vlNikolaj/PesmeMolitvene/Nikolaj100219.htm

No. 587 (20 August 1714).
The Spectator (1711–1714)

The reference to Cassius is that of the character in William Shakespeare's play Julius Caesar. Listen to an mp3 sound file http://www.otr.com/murrow_mccarthy.shtml of parts of this statement.
See It Now (1954)
Context: No one familiar with the history of this country can deny that congressional committees are useful. It is necessary to investigate before legislating, but the line between investigating and persecuting is a very fine one and the junior Senator from Wisconsin has stepped over it repeatedly. His primary achievement has been in confusing the public mind as between the internal and the external threats of communism. We must not confuse dissent with disloyalty. We must remember always that accusation is not proof and that conviction depends upon evidence and due process of law. We will not walk in fear, one of another. We will not be driven by fear into an age of unreason, if we dig deep in our history and our doctrine, and remember that we are not descended from fearful men — not from men who feared to write, to speak, to associate and to defend causes that were, for the moment, unpopular. This is no time for men who oppose Senator McCarthy's methods to keep silent, or for those who approve. We can deny our heritage and our history, but we cannot escape responsibility for the result. There is no way for a citizen of a republic to abdicate his responsibilities. As a nation we have come into our full inheritance at a tender age. We proclaim ourselves, as indeed we are, the defenders of freedom, wherever it continues to exist in the world, but we cannot defend freedom abroad by deserting it at home. The actions of the junior Senator from Wisconsin have caused alarm and dismay amongst our allies abroad, and given considerable comfort to our enemies. And whose fault is that? Not really his. He didn't create this situation of fear; he merely exploited it — and rather successfully. Cassius was right. "The fault, dear Brutus, is not in our stars, but in ourselves." Good night, and good luck.

Letter to William Strahan (1745); reported in Bartlett's Familiar Quotations, 10th ed. (1919).
Epistles