Taittiriyaka-Upanishad: First Valli, Eighth Anuvaka
1. Om means Brahman. 2. Om means all this. 3. Om means obedience. When they have been told, “Om, speak,” they speak. 4. After Om they sing Samans. 5. After Om they recite hymns. 6. After Om the Adhvaryu gives the response. 7. After Om the Brahman-priest gives orders. 8. After Om he (the sacrificer) allows the performance of the Agnihotra. 9. When a Braahmana is going to begin his lecture, he says, 10. “Om, may I acquire Brahman (the Veda).” He thus acquires the Veda.