Civilization is when old men plant trees in whose shade they will never sit.

 I first heard it as "Civilization is when old men plant trees in whose shade they will never sit."  The idea being that the current generation lays the groundwork for the well-being of the next.  That we selflessly take actions at cost to ourselves in order to benefit others in the future.  

The concept has always appealed to me.

Over the years, I have seen dozens of variations focusing on civilization, community, generosity, etc.   I finally checked in with Quote Investigator to find out whether this was a general adage in English or some other country (Greece and Turkey seemed to be candidates) or whether it was an attributable quote.  Or whether, as often happens, it is simply a general concept which keeps getting refined by many parties over time and the quote is whatever is received most commonly.

The latter.  

It has been attributed to many countries and to many individuals and there are many sources who come close but there is no settled formulation.  

Among ancient sources, CICERO Cato Major vii. 24 is pretty close. 

‘serit arbores, quae alteri saeclo prosint,’ ut ait Statius noster in Synephebis,

‘he plants trees, which will be of use to another age,’ as [Caecilius] Statius says in his Synephebi.

 I still prefer "Civilization is when old men plant trees in whose shade they will never sit."