Yesterday I told of some lines which occurred to me maybe a half dozen years ago that demanded "filling out"—at least the addition of a matching couplet to round out the meaning.
Some others have been in my mind since the days of Paul Carroll's undergraduate poetry workshop, that have cried for not merely a matching set of lines but the stanzas of an entire poem:
While the course of time shall run
We fall like shadows by the sun
Distributed upon his flight
Between the morning and the night.