Your soul is supposed to be perfect and divine. So why would you need to cleanse anything made from divine substance? Isn’t your perfect essence beyond the need for fixing or cleaning?
Well, it depends how you define Perfection.
Consider how your soul essence has experience after experience, lifetime after lifetime. Every experience leaves its imprint, like a muddy shoe print on your doormat. For example, that situation where you fell off a cliff in one lifetime left a bruise in your soul; the impact is still there, at a subtle level. And then, there was that situation where you were chased by the townspeople because you were a member of the wrong class, or religion, or tribe — that imprint is still there.