Why does the speaker repeat the following two lines Something there is that doesn't love a wall Good fences make good neighbors?

The speaker repeats the lines "Something there is that doesn't love a wall" and "Good fences make good neighbors" to emphasize the tension between natural forces that resist barriers and the human desire for boundaries. This repetition underscores the poem's exploration of the complexity of relationships and the necessity of maintaining personal space while acknowledging the inherent conflicts that arise from isolation. It highlights the paradox of needing walls for harmony while recognizing their potential to create division.