“What pity is it
That we can die but once to serve our country!”

Sylphs
Poems (1851), Prometheus

1960s, The American Promise (1965)

Speech to Labour Party fund-raising dinner, 11 May 1994 (the night before his death).

Speech at the First World Congress on Literacy (2 February 2005) paraphrasing a line in John Milton's Paradise Lost; quoted in Granma

"In the long history of the world, only a few generations have been granted the role of defending freedom in its hour of maximum danger. I do not shrink from this responsibility — I welcome it." is one of seven quotes inscribed on the walls at the gravesite of John F. Kennedy at Arlington National Cemetery.
"The energy, the faith, the devotion which we bring to this endeavor will light our country and all who serve it — and the glow from that fire can truly light the world." is one of seven quotes inscribed on the walls at the gravesite of John F. Kennedy at Arlington National Cemetery.
"And so, my fellow Americans: ask not what your country can do for you — ask what you can do for your country. My fellow citizens of the world: ask not what America will do for you, but what together we can do for the freedom of man." is one of seven quotes inscribed on the walls at the gravesite of John F. Kennedy at Arlington National Cemetery.
It has been reported at various places on the internet that in JFK's Inaugural address, the famous line "Ask not what your country can do for you, ask what you can do for your country", was inspired by, or even a direct quotation of the famous and much esteemed writer and poet Khalil Gibran. Gibran in 1925 wrote in Arabic a line that has been translated as:
::Are you a politician asking what your country can do for you or a zealous one asking what you can do for your country?
::If you are the first, then you are a parasite; if the second, then you are an oasis in a desert.
However, this translation of Gibran is one that occurred over a decade after Kennedy's 1961 speech, appearing in A Third Treasury of Kahlil Gibran (1975) edited by Andrew Dib Sherfan, and the translator most likely drew upon Kennedy's famous words in expressing Gibran's prior ideas. For a further discussion regarding the quote see here.
1961, Inaugural Address
Context: In the long history of the world, only a few generations have been granted the role of defending freedom in its hour of maximum danger. I do not shrink from this responsibility — I welcome it. I do not believe that any of us would exchange places with any other people or any other generation. The energy, the faith, the devotion which we bring to this endeavor will light our country and all who serve it — and the glow from that fire can truly light the world.
And so, my fellow Americans: ask not what your country can do for you — ask what you can do for your country.
My fellow citizens of the world: ask not what America will do for you, but what together we can do for the freedom of man.

Remarks by el-Sisi during a military conference (28 April 2013) http://www.youtube.com/watch?v=LC93fn9s3-c.
2013

Exclusive — Robert Wilkie: Democrats Want to Rewrite VA Motto to Remove Language from Lincoln’s Second Inaugural https://www.breitbart.com/radio/2021/05/31/va-robert-wilkie-abraham-lincoln-second-inaugural-veterans-affairs/ (31 May 2021)

The Secret of the Machines, Stanza 7.
Other works
Context: But remember, please, the Law by which we live,
We are not built to comprehend a lie,
We can neither love nor pity nor forgive,
If you make a slip in handling us you die!
We are greater than the Peoples or the Kings—
Be humble, as you crawl beneath our rods!—
Our touch can alter all created things,
We are everything on earth—except The Gods!

Tuesdays with Morrie (1997)