 what while we slept,
This side, that side hurling a heavyheaded hundredfold
What while we, while we slumbered.
O then, weary then whý should we tread? O why are we so
 haggard at the heart, so care-coiled, care-killed, so fagged,
 so fashed, so cogged, so cumbered,
When the thing we freely fórfeit is kept with fonder a care,
Fonder a care kept than we could have kept it, kept
Far with fonder a care (and we, we should have lost it) finer, fonder
A care kept. Where kept? Do but tell us where kept, where.—
Yonder.—What high as that! We follow, now we follow.—
 Yonder, yes yonder, yonder,
Yonder.
Stated once more, with finality.  Not the fading of an echo, but the beginning. 
 Repeating a word at the end of a poem to increase its impact is another favorite technique of Hopkins.  He does this in  That Nature is a Heraclitean Fire and of the comfort of the Resurrection