The speaker has arrived to "turn the grass" after someone else mowed it much earlier in the morning, "before the sun" had fully risen and the grass was still damp with dew. This turning is part of the process of making hay; it's the speaker's job to flip the grass over so that it will dry out.
This job does not require him to see the mower, who is long gone by the time the speaker comes to "view the levelled [that is, freshly cut] scene." And as the speaker looks out, presumably on a field or some other expanse of grass, and the reader perhaps already gets a sense of his loneliness as he prepares to do his job.
The sounds of these lines elevate the speaker's direct, straightforward language, infusing the lines with gentle music. Note the assonance, consonance, and alliteration of lines 3-4, for example:
The dew was gone that made his blade so keen
Before I came to view the levelled scene.
There's even an internal rhyme here between "made" and "blade," that combines with the ringing sharpness of the word "keen" to make the mower's gleaming scythe vivid for the reader (a scythe is sharp tool used to cut grass—there were no riding mowers in Frost's time!).
The poem also quickly establishes an orderly rhythm with the use of iambic pentameter. This means there are five iambs per line, poetic feet made up of an unstressed syllable followed by a stressed syllable: da-DUM. When read aloud, the poem thus has a pleasantly bouncy rhythm to it:
I went | to turn | the grass | once af- | ter one
Who mowed | it in | the dew | before | the sun.
Notice that the use of iambs isn't entirely strict: the second foot in the second line contains two unstressed beats, for example. But for the most part, the poem follows this unstressed-stressed rhythm closely, creating a measured, and maybe even soothing, tone. The use of the word "once" in the first line of the poem suggests the upcoming narrative arc of the poem: it rings faintly of "once upon a time," alerting the reader to the poem's intention of telling a story.
The poem's rhyme scheme also becomes quickly apparent: each stanza is a rhyming couplet. More specifically, they're something called heroic couplets (rhyming pairs of iambic pentameter):
- Heroic couplets were made famous by Chaucer and later used by 17th and 18th century poets writing about the heroic deeds of great men.
- This history lends an interesting undercurrent to this poem about a man who is simply getting ready to turn the grass to dry: clearly there's more at stake in this poem than what immediately presents itself in these opening lines.
- And, as the name suggests, the heroic couplet form means that these lines are bound together by rhythm and rhyme that ring out loudly and clearly to readers.