Om is the Akshara, or imperishable syllable. Om is the Universe, and this is the exposition of Om. The past, the present and the future, all that was, all that is, all that will be, is Om. Likewise, all else that may exist beyond the bounds of time, that too is Om. — Mandukya Upanishad
Om is the sacred sound of Brahman. Of all the Vedic verses (Mantras) the most powerful and significant one is the single-syllable incantation called Pranava. The Pranava or OM is the universally accepted symbol of Hinduism, Vedic culture. Literally the word Pranava means “That by which God is effectively praised.” It also means, “That which is ever new.”
Pranava or Om has been extolled highly in the Vedas, the Upanishads and the Bhagavad-gita as also in other scriptures. It is believed one’s own beastly nature may be conquered by repeatedly chanting OM.
The Yajur-Veda exhorts us to try to realize Brahman through repeating and remembering OM. The Kathopanishad declares that Om is Parabrahman (the Absolute Self) Itself. The Mandukyopanishud advises the spiritual aspirants to meditate on the unity of the Atman (the self) with Brahman (God) using OM for Japa (repeated chanting). Shri Krishna states in the Geeta that He is OM among words and that all religious rites are started with the chanting of OM. Not only that, if anyone succeeds in chanting OM at the time of his death, simultaneously thinking of God, he will attain the highest Truth. The Yoga Sutras of Patanjali declare that Pranava is the symbol of God and that one can attain Samadhi by its repetition, and meditation on Him.
The symbol Om is used for invocation, benediction, ritual worship, festivals, and religious ceremonies. It represents five separate sounds: ‘A’ ‘U’ ‘M’ plus the nasalization and resonance of the sound. It is said that within the ‘AUM’, Vishnu is ‘A’, Brahma is ‘U’ and Shiva is ‘M’; bindu (dot) is the trinity in unity while the nada (crescent) symbolizes transcendence. In the Upanishads, however, AUM is the symbol of the nirguna (formless) Brahman, without attributes, beyond human consciousness and duality (pranava).
Also, AUM is expressed as consisting of three independent letters A, U, and M, each of which has its own meaning and significance. The letter ‘A’ represents the beginning (Adimatwa), ‘U’ represents progress (Utkarsha) and ‘M’ represents limit or dissolution (Miti). Hence the word AUM represents that Power responsible for creation, development and dissolution of this Universe, namely God Himself. The first manifesting word of God is Om.
Om (aum) became the sacred word hum of the Tibetans, amin of the Moslems, and amen of the Egyptians, Greeks, Romans, and Christians. Amen in Hebrew means – sure, faithful. The biblical passage, John 1:1, “In the beginning was the Word, and the Word was with God, and the Word was God.” The New Testament declares that in the beginning God was the Word. According to the Bible, then, this means the pure sound vibration, or Shabda Brahman, from which all things manifest, including the eternal spiritual knowledge.
As a translator and scholar of Bagavad Gita, Barbara S. Miller notes, “According to the ancient Indian traditions preserved in the Upanishads, all speech and thought are derived from the one self-existent sound – Om. It expresses the ultimate reality.” Also, Georg Feuerstein in “The Yoga Tradition” says: “The syllable of Om is held to be or to express the pulse of the cosmos itself. It was through meditative practice rather than intellectual speculation that the seers and sages of Vedic times arrived at the idea of a universal sound, eternally resounding in the universe, which they ‘saw’ as the very origin of the created world.” [A more thorough explanation of OM is described in my booklet “Meditation: A Short Course to Higher Consciousness.”]