How we cite our quotes:
Time and fevers burn away
Individual beauty from
Thoughtful children, and the grave
Proves the child ephemeral: (3-6)
The speaker here notes how the passing of time affects us all. Time erases the beauty of our childhood, and all children will grow up into adults who will die one day. We are all "ephemeral."
But in my arms til break of day
Let the living creature lie, (7-8)
Even though we will all die one day, the speaker notes that his beloved is alive now, at least until the break of day. The image of dawn breaking reminds us even more of the passing of time.
On the stroke of midnight pass
Like vibrations of a bell, (21-23)
The speaker brings up two symbols of time passing: a clock and a bell. These are two strong reminders that time is always ticking away, and that there's nothing we can do to stop it. Even the stable things in life – our certainty and our faithfulness – will pass as time passes. Nothing lasts forever. (He's really driving this point home, isn't he?)