Why does edgar allan poe repeat the line "of the bells, bells, bells" in the poem "the bells"

Written at the end of Poe's life, this incantatory poem examines bell sounds as symbols of four milestones of human experience—childhood, youth, maturity, and death. “The Bells” is composed of four stanzas of increasing length and is a showcase of onomatopoeia, alliteration, repetition, and assonance. He also uses these bells as a use of alliteration in the poem.