The rainbow has many different shades of meaning in the poem. On one level, this phenomenon symbolizes the wonder of nature in all its many beautiful manifestations. While commonplace and frequently observed, the rainbow never loses its specialness because of its iconic shape and coloring—and because its appearance is unpredictable. In the poem, the speaker holds on to the awed delight that rainbows inspired in him as a child, treasuring their similar effect on him in adulthood. The speaker’s heart “lifts up” in response to nature’s sublimity.

For Wordsworth’s contemporaries, the rainbow’s biblical meaning would also have been top of mind. In the Old Testament Book of Genesis, after wiping out all of humanity with a flood save Noah on his Ark, God creates a rainbow as a symbolic promise never to destroy the inhabitants of the Earth in this way again. The rainbow is thus connected with divine grace, safety, and the continuity of the human race—something Wordsworth evokes in the parallel constructions in Lines 3-5, which echo biblical commandments.

The continuity of human life in past, present, and future is a leading idea in the poem. This continuity is affirmed and anticipated. The speaker does not want to experience any radical breaks or discontinuities in his life.