Bhṛgu realizes the prāṇa-maya (Taittiriya Upanisad 3.3)
Deeper is the realization of the vital airs as the origin and maintainer of all. The vital airs accommodate the subtle body inside the heart, and move it from one body to the other.
Section 3: Bhṛgu realizes the prāṇa-maya
Deeper than the realization of food as the origin is the realization of the vital airs as the origin and maintainer of all. The vital airs accommodate the subtle body inside the heart, and move it from one body to the other. Prana thus moves and maintains the body, and brings consciousness into it. These vital airs are, in turn, also a manifestation of the Supreme Brahman.
Text 3.3.1
prāṇo brahmeti vyajānāt
prāṇāddhyeva khalvimāni bhūtāni jāyante, prāṇena jātāni jīvanti
prāṇam prayantyabhisamviśantīti, tad vijñāya
punareva varuṇam pitaramupasasāra, adhīhi bhagavo brahmeti
tam hovāca
tapasā brahma vijijñāsasva, tapo brahmeti
sa tapo’tapyata, sa tapastaptvā
From his austerities, he realized prāṇa as Brahman. From prāṇa, all beings arise. By prāṇa, they are maintained, and into prāṇa, they enter at the time of death. Having understood this, he again inquired from his exalted father: "Please teach me more about Brahman." The father answered: "Search for Brahman in austerity. This austerity is Brahman." Bhṛgu again practiced austerities and further increased his spiritual realization.
Commentary: On SB 11.3.39 it is mentioned that prāṇo hi jīvam upadhāvati tatra tatra, “In all species of life the prāṇa, or vital air, remains unchanging and follows the spirit soul from one body to another”. However, in SB 4.28.24 it is mentioned that yadā tam evānu purī, viśīrṇā prakṛtim gatā, “As soon as they all left the city of the body, the five-hooded serpent (the five types of vital air) was immediately dismantled and smashed to dust”. In this way, it appears that prāṇa has two components: a gross component that is destroyed at the time of death, and a subtle component that carries the subtle body from one gross body to another, following the soul.
Because the soul is not observable by material means, being perceived only by the presence of consciousness, prāṇa is the only component that is observable when the soul leaves the body. It thus appears that at the time of death, the soul enters into prāṇa, or merges into prāṇa. The words "prāṇam prayantyabhisamviśantīti" are used in this sense. During life, the consciousness of the soul spreads over the whole body, but at death, this consciousness is withdrawn from the body and is carried by the vital air to the next body. Thus, it is said that the consciousness enters into prāṇa.