Brhadaranyaka Upanishad is the ancient and elementary or `Mukhya` part of Upanishad. It`s a commentary on Purush Sukta of the Vedas. It contains metaphors, symbolism and imagery for describing the nature of Reality. The First Chapter of Part Three of Brhadaranyaka Upanishad relates to the conversation between Yajnavalkya and Asvala. First Chapter of Part Four of Brhadaranyaka Upanishad deals with the partial definitions of Brahman. According to it Yajnavalkya arrived at the court of Janaka, the Emperor of Videha. Seeing him the emperor asked him the purpose of his visit. Yajnavalkya told him that he wished to ask some questions. He wished to hear what the teachers had told him about Brahman. Janaka told him that Jitvan, the son of Silina, taught him that the organ of speech (fire) is Brahman. Yajnavalkya then explained to him about the abode i.e. the body and the support of speech. He said that the physical organ of speech is its abode and its support is the akasa. It should thus be meditated upon as intelligence as the organ of speech. He told him that it is only through the organ of speech that the different Vedas like, the Rig Veda, the Yagur Veda, the Sama Veda, the Atharvangirasa and others like history, the Upanishads, explanations, verses, the arts, ancient lore, the results of sacrifices, commentaries, aphorisms, the results of giving food and drink, the result of offering oblations in the fire, this world, the next world and all beings can be achieved. The Supreme Brahman is the organ of speech. One who knows this and meditates upon it is never departed from the Supreme Brahman.

Yajnavalkya next wanted to hear what the teachers had further instructed the Emperor about the Brahman. The Emperor told him that Udanka, the son of Sulba had taught him that the vital breath (Prana) is Brahman. Yajnavalkya next explained him about the the abode i.e. the body and the support of Prana. He said that the vital breath is its abode and its support is the akasa. It should be meditated upon as dear i.e. the vital breath. It is the Supreme Brahman. It should thus be meditated upon. One who is aware of this is never departed from the Supreme Brahman.

Emperor Janaka on being asked again about Brahman said that Barku, the son of Vrishna had told him that the eye is Brahman. Yajnavalkya explained him about its abode and support. He told the king that the eye is its abode and the akasa is its support and should be meditated upon as truth. He told him that the truth is the eye and it is the Supreme Brahman. One who is aware of this and meditates upon him is never deserted by the Supreme Being.

Janaka next told him that Gardabhivipita, a descendant of Bharadvaja had taught him that the ear is Brahman. Yajnavalkya explained him about its abode and support. He told the king that its abode is the ear and its support is akasa. It should thus be meditated upon as infinite i.e. the quarters. He explains that to whatever quarter a person may go to, he can never reach its end. Thus, the quarters are infinite and are the Supreme Brahman. Yajnavalkya tells him that one who is aware of this and meditates upon it is never deserted by the Brahman.

The Emperor next narrated him that Satyakama, the son of Jabala, told him that the mind is Brahman. Yajnavalkya explained him about its abode and support. He told the Emperor that the mind is its abode and the akasa is its support. It should be meditated upon as bliss. He further explains that it is with the mind that a man wants and woos a woman. Then a son is to born to him who resembles him. He becomes the cause of Bliss. The mind is thus the cause of bliss and is the Supreme Brahman. Thus, the person who is aware of this and meditates upon it remains connected with the Supreme Brahman.

Yajnavalkya again asked him what more he had been taught about Brahman. The Emperor replied that Vidaghdha, the son of Sakala had taught him that the heart is Brahman. Yajnavalkya told him that the heart is its abode and the akasa is its support. It should be meditated upon as stability. The heart is the abode and support of all beings. It is the Supreme Brahman. It never deserts him who is aware of this and supports and meditates upon it.