Context

The poem's traveler pauses at dusk to watch a neighbor's woods fill with snow, tempted by their quiet darkness, before remembering his obligations. The poem closes by repeating its final line verbatim.

How the repetition works

Phrasal repetition — a multi-word unit repeated adjacently, functioning more like refrain or incantation than single-word emphasis. About this distinction →

The closing line is repeated exactly and adjacently, but the repetition is not mere emphasis: the first utterance reads literally (a long road still to travel) while the identical second utterance turns figurative, with 'sleep' shading toward death and the unfinished journey toward the obligations of a life. Phrasal epizeuxis here works by holding the words constant so only their meaning moves.