Brihadaranyaka Upanishad 1.3.22

1.3.22

eṣa u eva sāma vāgvai sāmaiṣa sā cāmaśceti tatsāmnaḥ sāmatvam | yadveva samaḥ pluṣiṇā samo maśakena samo nāgena sama ebhistribhirlokaiḥ samo'nena sarveṇa tasmādveva sāmāśnute sāmnaḥ sāyujyam̐ salokatāṃ ya evametatsāma veda

This is also Sâman. Speech is Sâ, and this is Ama. Because it is Sâ (speech) and Ama (vital force), therefore Sâman is so called. Or because it is equal to a white ant, equal to a mosquito, equal to an elephant, equal to these three worlds, equal to this universe, therefore this is Sâman. He who knows this Sâman (vital force) to be such attains union with it, or lives in the same world as it.