Whose woods these are I think I know.
His house is in the village though;
He will not see me stopping here
To watch his woods fill up with snow.
My little horse must think it queer
To stop without a farmhouse near
Between the woods and frozen lake
The darkest evening of the year.
He gives his harness bells a shake
To ask if there is some mistake.
After the practical description of the opening stanza Frost moves into a more spiritual state of mind.  “Between the woods and frozen lake” may allude to Dante’s  Inferno : specifically the “selva oscura” (dark wood) in which Dante’s pilgrim finds himself in middle age. Characteristic of Dante’s way of working, this “dark wood” is a product of the poet’s imagination. 
 See also the forest at the entrance to the classical underworld as described by Virgil in  Aeneid : 6.179 . Augustine’s association of sin with a “region of unlikeness”  ( Confessions : 7.10)  and the dangerous forests from which the wandering knights of medieval romances must extricate themselves may also come into play here. 
 These allusions place the speaker in the disconcerting, liminal space between the dark forest, which begins the descent into the infernal regions, and the frozen lake, which serves as  Inferno’s  Telos.  (XXXII-IV) 
 Horses are often said to have a sixth sense that  pick up their riders' anxieties . The speaker  antropomorphizes  the horse, suggesting that it  ‘sees’ this act of stopping as ‘queer’.  The horse, in this context, appears to retain its ‘sensibilities’ and ‘work ethic’ in the face of the haunting beauty of the wood, yet can’t comprehend why the narrator has forced it to stop because it can’t comprehend the sublime. 
 In reaility, as far as humans can judge, animals react rather than ‘think’. There is, however, a sense of communion between the speaker and the horse. Note that the adjective ‘little’ conveys a sense of care and affection by the speaker. The idea that the ‘little’ horse and the narrator conduct this silent conversation suggests the speaker has moved into a world of imagination, spirituality and symbolism. 
 One interpretation is that these lines may suggest that the rider is not only contemplating death but suicide. This, however, was challenged and dismissed with scorn by Robert Frost, as the next annotation explains. 

Stopping by Woods on a Snowy Evening