“To ask if there is some mistake” — What is the mistake referred to in Robert Frost’s poem “Stopping by woods on a snowy evening”?
The mistake is about stopping at an unusual place. As the speaker had never stopped in the woods before, he felt the horse might be thinking it to be a mistake or a result of something problematic. This thought of the speaker is triggered by the shaking of the harness bells of the horse, as if it is asking its owner whether there is some mistake. But it was actually a deliberate stop from the speaker.
But from a symbolic point of view this ‘mistake’ is the mistake of getting distracted by the temptations of life. In our journey of life, we often stop to watch rather petty things forgetting the responsibilities in our hand.