This text comes from The Poetical Works of John Keats, a historical songbook transcribed on Wikisource and reproduced from the pinned revision linked below.
In a drear-nighted December,
Too happy, happy tree,
Thy branches ne'er remember
Their green felicity:
The north cannot undo them,
With a sleety whistle through them;
Nor frozen thawings glue them
From budding at the prime.
In a drear-nighted December,
Too happy, happy brook,
Thy bubblings ne'er remember
Apollo's summer look;
But with a sweet forgetting,
They stay their crystal fretting,
Never, never petting
About the frozen time.
Ah! would 'twere so with many
A gentle girl and boy!
But were there ever any
Writhed not at passed joy?
To know the change and feel it,
When there is none to heal it,
Nor numbed sense to steal it,
Was never said in rhyme.