The Taittiriya Upanishad belongs to Krishna Yajur Veda and is part of the Taittiriya Aranyaka This Upanishad has three sections or Vallis. The first section discusses certain prerequisites for the study of Brahmavidya. The second and third sections discuss Brahmavidya.
The first section begins by mentioning the science of pronunciation or siksha such as sound, pitch, quality, force, modulation and combination etc. The spiritual significance of these is to show the presence of God in them. One of the verses mentions the spiritual abilities one must have to acquire the Higher Knowledge like ‘may my body be competent, may my tongue be sweet, let my ears listen to great things, let my knowledge be protected from evil.’ This verse also invokes Indra to bestow the sacred wisdom. In some of the verses a teacher appeals to God to send his good students with good conduct, temper, intelligence and coming from many lineages. There is an exposition of bhuh, bhuvah, svah and mahah. The presence of Aniruddha, Pradyumna, etc. in them is explained. The significance of AUM conveying the Saguna (countless attributes) of Brahman is especially brought. It is also stated that AUM conveys not only the original form but also all the incarnated forms of the Supreme Being. Towards the end of this section there are verses that are instructions to students who have completed their education. Following are some of the instructions:
One must speak the truth and practice dharma. One must continue the study of the scriptures. Prosperity in both worldly and otherworldly affairs must be kept in mind. Mother, father, teacher and guest must be treated as God. Wealth must be given away in charity in proportion to one’s means and must be performed with humility and with a deep sense of service to humanity. In case of doubts with respect to any specific action or a code of conduct, one has to seek guidance from the learned and the wise. Elders should be followed only when they are themselves in the right.
The second section begins with the description of Brahman. This Transcendental Self is covered here in the world of relativity by five distinct sheaths: annamaya kosa, the gross physical sheath; pranamaya kosa, the sheath of the vital force; manomaya kosa, the mental sheath; vijnanamaya kosa, the sheath of the advanced and developed knowledge; and anandamaya kosa, the sheath of Bliss. There are three types of bodies corresponding to these five sheaths. These bodies are called sthulasarira, suksmasarira and karanasarira. Sthula means ‘gross physical’ and sarira means ‘body’. Suksmasarira means ‘subtle body’ and karanasarira means ‘causal body’. The gross physical body comprises annamaya kosa; the subtle body comprises pranamaya kosa, manomaya kosa and vijnanamaya kosa. The Causal body comprises anandamaya kosa.
One of the most important attributes of Brahman is brought out in this section. Brahman is considered to be the source of all. He not only created every thing but also entered into it. This conveys the limitless nature of God with respect to space, time and attributes.
The last section is also called the Bhriguvalli. Here Brahman is described to be covered with eight sheaths – five as stated before and three more chakshurmaya, shrotrumaya and vagmaya. Sage Bhrigu through penance realizes these eight forms of God. Certain methods of worship such as kshema, yogakshema, etc. and bala, yashas, etc. are also explained.