“Our youth we can have but to-day,
We may always find time to grow old.”

Youth and Age http://whitewolf.newcastle.edu.au/words/authors/C/CloughArthurHugh/verse/poemsproseremains/youthage.html, st. 1.

2013, Cape Town University Address (June 2013)
Context: We always have the opportunity to choose our better history. We can always understand that most important decision -- the decision we make when we find our common humanity in one another. That’s always available to us, that choice. [... ] it can be heard in the confident voices of young people like you. It is that spirit, that innate longing for justice and equality, for freedom and solidarity -- that’s the spirit that can light the way forward. It's in you.

Source: The Walk

Multitude: War and Democracy in the Age of Empire

Source: Dictionary of Burning Words of Brilliant Writers (1895), P. 287.

Interview with Oriana Fallaci as reported in The Chicago Tribune (24 June 1973) (Excerpts online) http://www.jah-rastafari.com/selassie-words/show-jah-word.asp?word_id=int_ori.
Context: It is obvious that We have been young. We weren't born old! We have been a child, a boy, a youth, an adult, and finally an old man. Like everyone else. Our Lord the Creator made us like everyone else. Maybe you wish to know what kind of youth We were. Well We were a very serious, very diligent, very obedient youth. We were sometimes punished, but do you know why? Because what We were made to study did not seem enough and We wished to study further. We wanted to stay on at school after lessons were over. We were loath to amuse ourselves, to go riding, to play. We didn't want to waste time on games.

Mycetes, Act I, scene i, line 68
Tamburlaine (c. 1588)

Letter to http://memory.loc.gov/cgi-bin/query/r?ammem/mtj:@field(DOCID+@lit(tj110158)) Thomas Leiper (12 June 1815). Published in The Works of Thomas Jefferson in Twelve Volumes http://oll.libertyfund.org/ToC/0054.php, Federal Edition, Paul Leicester Ford, ed., New York: G. P. Putnam's Sons, 1904, Vol. 11 http://oll.libertyfund.org/Texts/Jefferson0136/Works/0054-11_Bk.pdf, pp. 477–478.
The sentence "I hope our wisdom will grow with our power, and teach us, that the less we use our power, the greater it will be." was used by US-President Barack Obama in his A New Beginning Speech.
1810s
Context: We concur in considering the government of England as totally without morality, insolent beyond bearing, inflated with vanity and ambition, aiming at the exclusive dominion of the sea, lost in corruption, of deep-rooted hatred towards us, hostile to liberty wherever it endeavors to show its head, and the eternal disturber of the peace of the world. In our estimate of Bonaparte, I suspect we differ. [... ] Our form of government is odious to him, as a standing contrast between republican and despotic rule; and as much from that hatred, as from ignorance in political economy, he had excluded intercourse between us and his people, by prohibiting the only articles they wanted from us, that is, cotton and tobacco. Whether the war we have had with England, and the achievements of that war, and the hope that we may become his instruments and partisans against that enemy, may induce him, in future, to tolerate our commercial intercourse with his people, is still to be seen. For my part, I wish that all nations may recover and retain their independence; that those which are overgrown may not advance beyond safe measures of power, that a salutary balance may be ever maintained among nations, and that our peace, commerce, and friendship, may be sought and cultivated by all. It is our business to manufacture for ourselves whatever we can, to keep our markets open for what we can spare or want; and the less we have to do with the amities or enmities of Europe, the better. Not in our day, but at no distant one, we may shake a rod over the heads of all, which may make the stoutest of them tremble. But I hope our wisdom will grow with our power, and teach us, that the less we use our power, the greater it will be.