How does the horse express the personal in "Stopping by Woods on a Snowy Evening"?

The horse is made personal through personification, and he also helps express the speaker’s thoughts and feelings, as well as emphasize his separateness from other people. As the poem begins, the reader does not know if the first-person speaker is alone or accompanied. The speaker’s gender is not indicated. They state, “I think I know” whose woods they are in or near. Their reference to the horse provides additional context and location, that they are between the woods and a lake, not near a dwelling.
The speaker also indicates possession and affection by saying, “My little horse.” A close relationship with the horse and an implication that no other human accompanies the speaker are also suggested. Instead of a person’s comments on the strangeness of the situation, the horse’s probable thoughts are provided. In the way they personify and humanize the horse, the speaker indicates their closeness: “My little horse must think it queer” and “He gives his harness bells a shake / To ask if there is some mistake.” The uncertainty or possible error of stopping at this spot are emphasized by drawing the horse into the commentary. The speaker begins by saying that the owner “will not mind” them stopping by his woods, but then has the horse imply what they are doing is “queer” or “a mistake.” The speaker projects their uncertainty onto their only companion, the little horse.
https://www.poetryfoundation.org/poems/42891/stopping-by-woods-on-a-snowy-evening