Here's Walt Whitman's poem "The Voice of the Rain"
And who art thou? said I to the soft-falling shower,
Which, strange to tell, gave me an answer, as here translated:
I am the Poem of Earth, said the voice of the rain,
Eternal I rise impalpable out of the land and the bottomless sea,
Upward to heaven, whence, vaguely form'd, altogether changed, and yet the same,
I descend to lave the drouths, atomies, dust-layers of the globe,
And all that in them without me were seeds only, latent, unborn;
And forever, by day and night, I give back life to my own origin, and make pure and beautify it;
(For song, issuing from its birth-place, after fulfilment, wandering
Reck'd or unreck'd. duly with love returns.)
What does Whitman mean by the last two lines?