`Let all things pass away.'

A rivery field spread out below,
An odour of the new-mown hay
In his nostrils, the great lord of Chou
Cried, casting off the mountain snow,
`Let all things pass away.'

Wheels by milk-white asses drawn
Where Babylon or Nineveh
Rose; some conquer drew rein
And cried to battle-weary men,
`Let all things pass away.'

From man's blood-sodden heart are sprung
Those branches of the night and day
Where the gaudy moon is hung.
What's the meaning of all song?
`Let all things pass away.'

William Butler Yeats