There was never a sound beside the wood but one,
And that was my long scythe whispering to the ground.
What was it it whispered? I knew not well myself;
Perhaps it was something about the heat of the sun,
Something, perhaps, about the lack of sound—
And that was why it whispered and did not speak.
The poet asks a  rhetorical  question. The conversational tone is typical of Frost, The reader is drawn in to his speculation.
Mowing