The transcendental vibration omkara is explained in the Bhagavad-gita, Chapter Eight, verse thirteen:

If one actually understands that omkara is the sound representation of the Supreme Personality of Godhead, whether he chants omkara or the Hare Krsna mantra, the result is certainly the same.

The transcendental vibration of omkara is further explained in the Bhagavad-gita, Chapter Nine, verse seventeen:

Similarly, the transcendental sound om is further explained in the Bhagavad-gita, Chapter Seventeen, verse twenty-three:

Throughout all the Vedic scriptures the glories of omkara are specifically mentioned. Srila Jiva Gosvami, in his thesis Bhagavat-sandarbha, says that in the Vedic literature omkara is considered to be the sound vibration of the holy name of the Supreme Personality of Godhead. Only this vibration of transcendental sound can deliver a conditioned soul from the clutches of maya. Sometimes omkara is also called the deliverer (tara). Srimad-Bhagavatam begins with the omkara vibration: om namo bhagavate vasudevaya. Therefore omkara has been described by the great commentator Sridhara Svami as tarankura, the seed of deliverance from the material world. Since the Supreme Godhead is absolute, His holy name and His sound vibration omkara are as good as He Himself. Caitanya Mahaprabhu says that the holy name, or omkara, the transcendental representation of the Supreme Personality of Godhead, has all the potencies of the Personality of Godhead.

On the basis of all the Upanisads, Srila Jiva Gosvami says that omkara is the Supreme Absolute Truth and is accepted as such by all the acaryas and authorities. Omkara is beginningless, changeless, supreme and free from deterioration and external contamination. Omkara is the origin, middle and end of everything, and any living entity who thus understands omkara attains the perfection of spiritual identity in omkara. Omkara, being situated in everyone's heart, is isvara, the Supreme Personality of Godhead, as confirmed in the Bhagavad-gita (18.61): isvarah sarva-bhutanam hrd-dese 'rjuna tisthati. Omkara is as good as Visnu because omkara is as all-pervasive as Visnu. One who knows omkara and Lord Visnu to be identical no longer has to lament or hanker. One who chants omkara no longer remains a sudra but immediately comes to the position of a brahmana. Simply by chanting omkara one can understand the whole creation to be one unit, or an expansion of the energy of the Supreme Lord: idam hi visvam bhagavan ivetaro yato jagat-sthana-nirodha-sambhavah. "The Supreme Lord Personality of Godhead is Himself this cosmos, and still He is aloof from it. From Him only this cosmic manifestation has emanated, in Him it rests, and unto Him it enters after annihilation." (Bhag. 1.5.20) Although one who does not understand concludes otherwise, Srimad-Bhagavatam states that the entire cosmic manifestation is but an expansion of the energy of the Supreme Lord. Realization of this is possible simply by chanting the holy name of the Lord, omkara.

One should not, however, foolishly conclude that because the Supreme Personality of Godhead is omnipotent, we have manufactured a combination of letters-a, u and m-to represent Him. Factually the transcendental sound omkara, although a combination of the three letters a, u and m, has transcendental potency, and one who chants omkara will very soon realize omkara and Lord Visnu to be nondifferent. Krsna declares, pranavah sarva-vedesu: "I am the syllable om in the Vedic mantras." (Bg. 7.8) One should therefore conclude that among the many incarnations of the Supreme Personality of Godhead, omkara is the sound incarnation. All the Vedas accept this thesis. One should always remember that the holy name of the Lord and the Lord Himself are always identical (abhinnatvan nama-naminoh). Since omkara is the basic principle of all Vedic knowledge, it is uttered before one begins to chant any Vedic hymn. Without omkara, no Vedic mantra is successful. The Gosvamis therefore declare that pranava (omkara) is the complete representation of the Supreme Personality of Godhead, and they have analyzed omkara in terms of its alphabetical constituents as follows:

The Mayavadi philosophers consider many Vedic mantras to be the maha-vakya, or principal Vedic mantra, such as tat tvam asi (Chandogya Upanisad 6.8.7), idam sarvam yad ayam atma and brahmedam sarvam (Brhad-aranyaka Upanisad 2.5.1), atmaivedam sarvam (Chandogya Upanisad 7.25.2) and neha nanasti kincana (Katha Upanisad 2.1.11). That is a great mistake. Only omkara is the maha-vakya. All these other mantras that the Mayavadis accept as the maha-vakya are only incidental. They cannot be taken as the maha-vakya, or maha-mantra. The mantra tat tvam asi indicates only a partial understanding of the Vedas, unlike omkara, which represents the full understanding of the Vedas. Therefore the transcendental sound that includes all Vedic knowledge is omkara (pranava).

Aside from omkara, none of the words uttered by the followers of Sankaracarya can be considered the maha-vakya. They are merely passing remarks. Sankaracarya, however, has never stressed chanting of the maha-vakya omkara; he has accepted only tat tvam asi as the maha-vakya. Imagining the living entity to be God, he has misrepresented all the mantras of the Vedanta-sutra with the motive of proving that there is no separate existence of the living entities and the Supreme Absolute Truth. This is similar to the politician's attempt to prove nonviolence from the Bhagavad-gita. Krsna is violent to demons, and to attempt to prove that Krsna is not violent is ultimately to deny Krsna. As such explanations of the Bhagavad-gita are absurd, so also is Sankaracarya's explanation of the Vedanta-sutra, and no sane and reasonable man will accept it. At present, however, the Vedanta-sutra is misrepresented not only by the so-called Vedantis but also by other unscrupulous persons who are so degraded that they even recommend that sannyasis eat meat, fish and eggs. In this way Sankara's so-called followers, the impersonalist Mayavadis, are sinking lower and lower. How can these degraded men explain the Vedanta-sutra, which is the essence of all Vedic literature?

Lord Sri Caitanya Mahaprabhu has declared, mayavadi-bhasya sunile haya sarva-nasa: "Anyone who hears commentary on the Vedanta-sutra from the Mayavada school is completely doomed." As explained in the Bhagavad-gita (15.15), vedais ca sarvair aham eva vedyah: all Vedic literature aims to understand Krsna. Mayavada philosophy, however, has deviated everyone from Krsna. Therefore there is a great need for the Krsna consciousness movement all over the world to save the world from degradation. Every intelligent and sane man must abandon the philosophical explanation of the Mayavadis and accept the explanation of Vaisnava acaryas. One should read Bhagavad-gita As It Is to try to understand the real purpose of the Vedas.