Closing line of
杜秋娘《
金缕衣》 (Du Qiuniang, attrib., Tang, c. 9th c.):
劝君莫惜金缕衣,
劝君惜取少年时。
花开堪折直须折,
莫待无花空折枝 (I urge you not to treasure the gold-threaded robe; I urge you to treasure your youthful years. When the flower blooms and may be plucked, just pluck it — don't wait till it's gone to break the empty branch). Du Qiuniang was a Tang courtesan-turned-consort; the poem is both carpe-diem advice and a warning about wasted opportunity.