This text comes from The Poetical Works of John Keats, a historical songbook transcribed on Wikisource and reproduced from the pinned revision linked below.
Spenser! a jealous honorer of thine,
A forester deep in thy midmost trees,
Did, last eve, ask my promise to refine
Some English, that might strive thine ear to please.
But, Elfin-poet! 'tis impossible
For an inhabitant of wintry earth
To rise, like Phœbus, with a golden quill,
Fire-winged, and make a morning in his mirth.
It is impossible to 'scape from toil
O' the sudden, and receive thy spiriting:
The flower must drink the nature of the soil
Before it can put forth its blossoming:
Be with me in the summer days, and I
Will for thine honor and his pleasure try.