Bhashya
तथा प्राणेन पञ्चवृत्तिना, रक्षन् परिपालयन्- अन्यथा मृतभ्रान्तिः स्यात्, अवरम् निकृष्टम् अनेकाशुचिसंघात- त्वादत्यन्तबीभत्सं, कुलायं नीडं शरीरम्, स्वयं तु बहि- स्तस्मात्कुलायात्, चरित्वा- यद्यपि शरीरस्थ एव स्वप्नं पश्यति तथापि तत्संबंधाभावात् तत्स्थ इव आकाशः बहि- श्चरित्वेत्युच्यते, अमृतः स्वयममरणधर्मा, ईयते गच्छति, यत्र कामम्- यत्र यत्र कामः विषयेषु उद्भूतवृत्तिर्भवति तं तं कामं वासनारूपेण उद्भूतं गच्छति ॥
In plain words
In the same way, the breath, working through its five channels, keeps this body alive — otherwise you would mistake it for a corpse. 'Low' means exactly that: base, because it is nothing but a heap of impurities, altogether repulsive. This body is the nest. But the self itself moves outside that nest, on its own. Even though, strictly speaking, he never leaves the body while dreaming, no real bond ties him to it — so the text says he 'moves outside,' the way space seems to sit inside a jar without ever being confined by it. 'Immortal' means: by nature, never subject to dying. 'Goes' simply means moves. And 'wherever it wishes' means this: wherever a desire flares up toward some object, he moves straight toward that very desire, now risen up in the shape of a buried impression.
Close to the Sanskrit
Likewise, protecting — sustaining — the body by means of the breath which functions in five ways: otherwise the mistaken notion that it is dead would arise. 'Low' means base, because, on account of being an aggregate of many impure things, it is utterly loathsome; the body is the 'nest,' the resting-place. The self itself, however, having moved outside, away from that nest — although he sees the dream while still situated in the body, nevertheless, since there is no real connection with it, it is said that 'he moves outside,' just as space, though seeming to be situated somewhere, is not confined there. 'Immortal' means by nature not subject to death. 'Goes' means moves. 'Wherever it wishes' means: wherever, among sense-objects, a desire arises as a mental impulse, toward that very desire, now arisen in the form of a latent impression, he goes.