This is one of the minor Upaniṣads belonging to the Kṛṣṇa Yajurveda. It is a fairly large work of 110 ślokas or verses in the anuṣṭubh meter. The Praṇava or Oṅkāra as also the Haṁsamantra (so’haṁ haṁsaḥ) are the main topics dealt with. However, the several details that are given, concerning the various aspects of meditation on these two mantras, make the work quite recondite.
The Upaniṣad starts with an exposition of Praṇava, its four parts and contem-plations connected with them. Just as the sound of a gong or a bell, made of bell-metal, gradually gets attenuated, finally merging into the infinite sound or infinite silence, the mind of a yogi who utters the Praṇava (Oṁ), lengthening it over sixteen mātrās or instants of time, simultaneously concentrating his mind on that sound, also gets dissolved in Brahman, the final goal of praṇava-japa.
Haṁsavidyā is the next topic taken up. The words ‘haṁ’ and ‘saḥ’ represent the jīvātman (the individual self) and Parmātman or Brahman (the Supreme Self) respectively. The natural breathing process of inhalation and exhalation should be mentally connected with the two words ‘haṁ’ and ‘saḥ’. Then the process of breathing itself gets converted into japa (repetition of divine name) ultimately resulting in the experience of the unity of the two. This is Haṁsavidyā.
After stressing that the ātman can be known only through the śruti (the scripture or the Vedas) and the ācārya (spiritual preceptor), the Upaniṣad goes on to describe three types of ācāryas—the codaka, the bodhaka and the mokṣada. Codaka is actually the Vedas which impel a person to take to the spiritual path. The bodhaka is the teacher who teaches the disciple, ‘Thou art That.’ Mokṣada (giver of liberation) is the Lord himself, since it is only he that can give mokṣa or liberation.
Here, the Upaniṣad declares that it is in the heart alone that one realises this ‘Haṁsa’ or the Lord who is the indwelling spirit.
The work concludes with a long, highly poetical, soliloquy by the knower of the Self, the gist of which is that he exists in all and is all.
See also UPANIṢADS.