The Brahmopaniṣad is a minor Upaniṣad and is assigned to the Kṛṣṇa Yajurveda. There seems to be two recensions—the South Indian and the North Indian. The latter is the longer version.
Śaunaka approaches the sage Pippa-lāda of the Aṅgiras-gotra and puts him a question regarding the location and functioning of the deities of the indriyas or sense-organs in the divine Brahmapura (the human body). In reply, Pippalāda imparts the excellent Brahmavidyā or spiritual wisdom concerning ātman/ Brahman.
It is prāṇa or ātman that exercises its power over all the devas or the indriyas (sense-organs). Situated in this Brahma-pura (the human body) it is the pure, resplendent, partless Brahman that controls these sense-organs.
When the jīva (prāṇa or ātman) goes out of the body during suṣupti or deep sleep, all the sense-organs also follow him even as the bees follow the queen bee. He moves about in sleep like an eagle flying freely in the sky. In this state of suṣupti the jīva is not tainted or affected by good and bad. He comes back to the waking state through the dream state.
This puruṣa (the jīva or the ātman bound in this body) has four seats where his presence is felt: nābhi (navel), hṛdaya (heart), kaṇṭha (throat) and mūrdhā (head). Associated with the four states of consciousness, viz., jāgrat (waking state), svapna (dream state), suṣupti (deep sleep state) and turīya (the fourth or the super-conscious state), he is known respectively as Brahmā, Viṣṇu, Rudra and Akṣara. But in himself he is pure Light, beyond the limitations of all the sense-organs.
At the cosmic level, since he is everything and all things are merged in him without distinction, the worlds, the gods, the sacrificial systems, all human relationships and varieties of human beings do not exist separately as distinguished from him.
The Upaniṣad then goes on to describe the real meaning of śikhā (tuft of hair) and yajñopavīta (sacred thread) as related to Brahman (the Absolute). The externals should be discarded and jñāna or knowledge (of the ātman) should take their place.
This is then followed by some verses which appear in other Upaniṣads like the Śvetāśvatara also. They describe the Supreme Lord as the all-pervading reality and also as residing in the hearts of all beings in a subtle form. He is the supreme witness, energiser, master-controller and supervisor. Those who realize him in their own hearts attain eternal happiness, and not the others.
Just as the fire which is inherent in the araṇis (attritional pieces of wood used in Vedic sacrifices to produce fire) is brought out by their attrition, or oil from the oil-seeds or butter from curds or water from the earth by proper means, the ātman inside us can be brought out, i.e., experienced, through meditation. Once this is done, the jīva or the individual soul is liberated from all types of bondage.
See also UPANIṢADS.