The whole John Donne meditation the title is referencing:

    No man is an island,
    Entire of itself;
    Every man 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 thy friend's
    Or of thine own were.
    
    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

Thanks for sharing!

In case anyone else is wondering why the meter is so awkward: It turns out that in the original this passage was prose, not poetry. Source: https://www.universitychurch.ox.ac.uk/sermons/devotions-upon...

Hemingway also borrowed the penultimate line in For Whom The Bell Tolls. I also had to memorize this back in the day but I still stop to read it whenever I see it somewhere.

Not totally related but The Tuft of Flowers by Robert Frost always reminds me Donne's poem.

  The Tuft of Flowers
  
  I went to turn the grass once after one
  Who mowed it in the dew before the sun.
 
  The dew was gone that made his blade so keen
  Before I came to view the levelled scene.
 
  I looked for him behind an isle of trees;
  I listened for his whetstone on the breeze.
 
  But he had gone his way, the grass all mown,
  And I must be, as he had been,—alone,
 
  ‘As all must be,’ I said within my heart,
  ‘Whether they work together or apart.’
 
  But as I said it, swift there passed me by
  On noiseless wing a ‘wildered butterfly,
 
  Seeking with memories grown dim o’er night
  Some resting flower of yesterday’s delight.
 
  And once I marked his flight go round and round,
  As where some flower lay withering on the ground.
 
  And then he flew as far as eye could see,
  And then on tremulous wing came back to me.
 
  I thought of questions that have no reply,
  And would have turned to toss the grass to dry;
 
  But he turned first, and led my eye to look
  At a tall tuft of flowers beside a brook,
 
  A leaping tongue of bloom the scythe had spared
  Beside a reedy brook the scythe had bared.
 
  I left my place to know them by their name,
  Finding them butterfly weed when I came.
 
  The mower in the dew had loved them thus,
  By leaving them to flourish, not for us,
 
  Nor yet to draw one thought of ours to him.
  But from sheer morning gladness at the brim.
 
  The butterfly and I had lit upon,
  Nevertheless, a message from the dawn,
 
  That made me hear the wakening birds around,
  And hear his long scythe whispering to the ground,
 
  And feel a spirit kindred to my own;
  So that henceforth I worked no more alone;
 
  But glad with him, I worked as with his aid,
  And weary, sought at noon with him the shade;
 
  And dreaming, as it were, held brotherly speech
  With one whose thought I had not hoped to reach.
 
  ‘Men work together,’ I told him from the heart,
  ‘Whether they work together or apart.’

I'm glad you posted this, because I only knew the last two sentences, and I had completely misunderstood the meaning.

I thought it was more of a warning, like an omen. It turns out it's closer to the Tao.