Please explain the following lines from "Ode to a Nightingale."
Thou wast not born for death, immortal Bird!
No hungry generations tread thee down;
The voice I hear this passing night was heard
In ancient days by emperor and clown:
Perhaps the self-same song that found a path...
As with any question that asks you to explain a certain part of a text or a poem, it is vital that you have a look at this excerpt within the context of the poem as a whole and not just try to guess at the meaning by looking at these lines in isolation. What is key to these lines is the way that they clearly point towards the nightingale being a symbol of the eternal beauty of nature and enduring art that makes it so separate from the experience of the speaker. The speaker says that the nightingale was not "born for death" and that there are no "hungry generations" who are trying to "tread thee down." Before these lines, the speaker has dwelled on the way that life for humans is characterised by suffering and pain. Focusing on the nightingale, the speaker now sees that this bird, and what it stands for, is free from this experience of suffering. The beauty of the nightingale's song is something that has endured throughout the ages, as it was heard "in ancient days by emperor and clown." Art and beauty, like the nightingale's song, is therefore something that endures the test of time in a way that humans cannot, but also penetrates every social sphere, both the great of the world (the emperors) as well as the foolish (the clowns).