Chiasmus is a balanced reversal of grammatical structure in two parallel phrases, so the second half mirrors the first in reverse order. It often creates emphasis, symmetry, and a memorable turn of thought. When the same words are repeated in the reversal, the device is a special form called antimetabole.
Figure of speech where the second half of a phrase reverses the order of the first half e.g. Samuel Johnson's "For we that live to please, must please to live."
Example
She came to break the silence, and to silence the breaking came.
He loved the mountain for its height, and its height for the way he loved it.