In plain words
So when man sleeps, only the five fires of the five prāṇas are awake. When man sleeps, the jīva itself enjoys that ease, that Ānanda, that happiness. What happened before, the things happening now, what he saw before, what he is seeing now, what he experienced before, what he is experiencing now: all these man experiences in the form of dreams. Not only this: because the saṃskāras of many births are also stamped within him, man is able to experience in dreams those too, forms he does not know, and matters too. So at the time of sleep the five prāṇas alone are awake. The ease, the Ānanda and the happiness of the state of sleep, the jīva itself enjoys. In the dream state he fashions everything himself, fashions even himself, and he himself goes on experiencing feelings that are contrived. Manas alone is the root cause of all this! Manaeva manuṣyāṇāṃ kāraṇaṃ bandhamokṣayoḥ. Of these two, of dream and of sleep, of the deep Ānanda, Manas alone is the root cause.
While he was giving this answer to Śaurāyani, the sixth disciple, Śibi, came in: Swami! The śāstras teach that men who keep contemplating the praṇava at their last moment attain the Akṣara. That is, the śāstras teach that a lasting abode comes to them. Can this be! Then Pippalāda: Child! Śibi! The whole world is filled with the praṇava. The praṇava is the very form of the Paramātma. Through the principle of a, u and m within the praṇava, it is the praṇava alone that pervades all and experiences these three worlds: this world called bhū, bhuvarloka, which stands at a higher level than this, and suvarloka, the highest level of all. To this very praṇava the Ṛgveda, the Yajurveda and the Sāmaveda too are dedicated. The sounds of these three Vedas too sing their refrain in the Oṃkāra alone. So these principles called bhūr, bhuvaḥ and suvar belong not only to the three worlds, not only to the three Vedas, but to the three mātrās as well. That is, a, u and m are the three mātrās. Bhūr, bhuvas and suvarloka are the three worlds. The Ṛgveda, the Yajurveda and the Sāmaveda are the three Vedas. All in all, the sound of the praṇava alone fills everything everywhere. This praṇava has another name, the form of the eight splendours: