“Why we should put ourselves out of our way to do anything for posterity, for what has posterity ever done for us?”

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

Alternate translation: We go to great pains to alter life for the happiness of our descendants and our descendants will say as usual: things used to be so much better, life today is worse than it used to be.
Мы хлопочем, чтобы изменить жизнь, чтобы потомки были счастливы, а потомки скажут по обыкновению: прежде лучше было, теперешняя жизнь хуже прежней.
Note-Book of Anton Chekhov (1921)

2013, Second Inaugural Address (January 2013)
Context: We, the people, still believe that our obligations as Americans are not just to ourselves, but to all posterity.  We will respond to the threat of climate change, knowing that the failure to do so would betray our children and future generations. Some may still deny the overwhelming judgment of science, but none can avoid the devastating impact of raging fires and crippling drought and more powerful storms. The path towards sustainable energy sources will be long and sometimes difficult. But America cannot resist this transition, we must lead it. We cannot cede to other nations the technology that will power new jobs and new industries, we must claim its promise. That’s how we will maintain our economic vitality and our national treasure -- our forests and waterways, our crop lands and snow-capped peaks. That is how we will preserve our planet, commanded to our care by God. That’s what will lend meaning to the creed our fathers once declared.

Ce qu'on appelle la postérité, c'est la postérité de l'œuvre.
Source: In Search of Lost Time, Remembrance of Things Past (1913-1927), Vol II: Within a Budding Grove (1919), Ch. I: "Madame Swann at Home"

1830s, The Lyceum Address (1838)
Context: We find ourselves under the government of a system of political institutions, conducing more essentially to the ends of civil and religious liberty, than any of which the history of former times tells us. We, when mounting the stage of existence, found ourselves the legal inheritors of these fundamental blessings. We toiled not in the acquirement or establishment of them; they are a legacy bequeathed us by a once hardy, brave, and patriotic, but now lamented and departed, race of ancestors. Theirs was the task (and nobly they performed it) to possess themselves, and through themselves us, of this goodly land, and to uprear upon its hills and its valleys a political edifice of liberty and equal rights; 'tis ours only to transmit these — the former unprofaned by the foot of an invader, the latter undecayed by the lapse of time and untorn by usurpation — to the latest generation that fate shall permit the world to know. This task gratitude to our fathers, justice to ourselves, duty to posterity, and love for our species in general, all imperatively require us faithfully to perform.

Knox on the Declaration of Independence. Reported in David McCullough, 1776 (2005), p. 83.

Original: (fr) L’important n’est pas ce qu’on fait de nous mais ce que nous faisons nous-même de ce qu’on a fait de nous.
Source: Saint Genet, Actor and Martyr (1952), p.55

Quoted in "Enter Japan" - "Time Magazine" article - July 8, 1940