“Ask not how long the term you will serve, but ask what meaningful things you will do during your tenure.”

"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.

Quoted in: Honor Books, ‎W. B. Freeman (2004), God's Little Devotional Book for Girls, p. 205
2000s

Firstpost, First Post http://www.firstpost.com/india/dont-us-politicians-ask-yourself-what-you-can-do-for-india-rahul-606481.html Gujarat Congress http://gujaratcongress.org/english/2013/02/rahul-gandhi-urges-youth-to-contribute-to-india%E2%80%99s-growth/ Rahul Gandhi http://my.fakingnews.firstpost.com/politics/inspiration-behind-rahul-gandhis-famous-quotes-5528

Posthumous attributions, Tupac: Resurrection (2003)

I ask you to be citizens: citizens, not spectators; citizens, not subjects; responsible citizens, building communities of service and a nation of character.
2000s, 2001, First inaugural address (January 2001)

2000s, 2001, First inaugural address (January 2001)

Testimony before subcommittees of the U.S. Senate, April, 1971