He gives his harness bells a shake To ask if there is some mistake.
The only other sound’s the sweep
Of easy wind and downy flake.

The woods are lovely, dark and deep,
But I have promises to keep,
And miles to go before I sleep,
And miles to go before I sleep.
Who has promises to keep in the passage from "Stopping by Woods on a Snowy Evening" by Robert Frost?

The man who owns the woods

The poet, Robert Frost

The horse shaking his harness

The anonymous speaker