Khandogya-Upanishad: First Prapathaka, First Khanda
1. Let a man meditate on the syllable Om, called the udgitha; for the udgitha (a portion of the Sama-veda) is sung, beginning with Om.
The full account, however, of Om is this:—
2. The essence of all beings is the earth, the essence of the earth is water, the essence of water the plants, the essence of plants man, the essence of man speech, the essence of speech the Rig-veda, the essence of the Rig-veda the Sama-veda, the essence of the Sama-veda the udgitha (which is Om).
3. That udgitha (Om) is the best of all essences, the highest, deserving the highest place, the eighth.
4. What then is the Rik? What is the Saman? What is the udgitha? This is the question.
5. The Rik indeed is speech, Saman is breath, the udgitha is the syllable Om. Now speech and breath, or Rik and Saman, form one couple.
6. And that couple is joined together in the syllable Om. When two people come together, they fulfil each other's desire.
7. Thus he who knowing this, meditates on the syllable (Om), the udgitha, becomes indeed a fulfiller of desires.
8. That syllable is a syllable of permission, for whenever we permit anything, we say Om, yes. Now permission is gratification. He who knowing this meditates on the syllable (Om), the udgitha, becomes indeed a gratifier of desires.
9. By that syllable does the threefold knowledge (the sacrifice, more particularly the Soma sacrifice, as founded on the three Vedas) proceed. When the Adhvaryu priest gives an order, he says Om. When the Hotri priest recites, he says Om. When the Udgatri priest sings, he says Om,—all for the glory of that syllable. The threefold knowledge (the sacrifice) proceeds by the greatness of that syllable (the vital breaths), and by its essence (the ablations).
10. Now therefore it would seem to follow, that both he who knows this (the true meaning of the syllable Om), and he who does not, perform the same sacrifice. But this is not so, for knowledge and ignorance are different. The sacrifice which a man performs with knowledge, faith, and the Upanishad is more powerful. This is the full account of the syllable Om.