in “the soul unto itself,” of what does the speaker say the soul should stand in awe?

In Emily Dickinson’s poem “The Soul unto itself,” the speaker says that the Soul should stand in awe of itself.

Quick explanation

At the end of the poem, Dickinson writes that the soul is “its Sovereign – of itself / The Soul should stand in Awe –,” which means the soul ought to be humbled and amazed by its own power and sovereignty. In other words, the thing the soul should revere and fear a little is its own inner nature and authority.

TL;DR: The soul should stand in awe of itself.