What is the Purpose of Human Life?

परोपकाराय फलन्ति वृक्षाः परोपकाराय वहन्ति नद्याः ।
परोपकाराय दुहन्ति गावः परोपकाराय शरीरम् एतत् ॥

paropakArAya phalanti vRukShAH paropakArAya vahanti nadyAH |
paropakArAya duhanti gAvaH paropakArAya sharIram etat ||

Meaning:
Trees give fruits to assist others. 
Rivers flow to do good to others. 
Cows produce to feed others. 
(In the same way,) our own body should be employed for the assistance of others.