For Whom The Bells Tolls

For Whom the Bell Tolls is a novel by Ernest Hemingway published in 1940. It tells the story of Robert Jordan, a young American volunteer attached to a Republican guerrilla unit during the Spanish Civil War. As a dynamiter, he is assigned to blow up a bridge during an attack on the city of Segovia.

No man is an island,
Entire of itself.
Each is a piece of the continent,
A part of the main.
If a clod be washed away by the sea,
Europe is the less.
As well as if a promontory were.
As well as if a manor of thine own
Or of thine friend's were.
Each man's death diminishes me,
For I am involved in mankind.
Therefore, send not to know
For whom the bell tolls,
It tolls for thee.

" No Man is an Island" 
 The phrase 'no man is an island' expresses the idea that human beings do badly when isolated from others and need to be part of a community in order to thrive. 

"If a clod be washed away by the sea, Europe is the less." Meaning that all humanity is one large unit created by God.

“Any man's death diminishes me, because I am involved in mankind; and therefore never send to know for whom the bell tolls; it tolls for thee.”