Taittiriya Upanishad is associated with Taittiriya recension of the Krishna Yajurveda. The seventh, eighth and ninth chapters of the Taittiriya Arantyaka is considered as Taittiriya Upanishad.
Theory of Oneness is the ultimate teaching of the Upanishad “ (When) the Soul attains self-sovereignty, becomes lord of the mind, it becomes lord of speech, the lord of the eyes, the lord of the ears, the lord of knowledge; then it becomes Brahman; its body is the boundless space, its essential nature is the reality, truth; its playground the life-force, its consciousness a state of bliss, it exists in serenity, in calmness, in peace, a state of immortality. (Taittiriya Upanishad, I.6.2)”
Taittiriya Upanishad is divided into three sections, ShikshaValli, BrahmanandaValli and Bhriguvalli.
ShikshaValli presents instructions for the aspirants and process for attainment of Brahma Jnana or the knowledge of the self.
The BrahmanandaVallienumerates with bliss of the Brahman.
The Bhriguvalli presents the knowledge of the Supreme Self.