OM is the Pranava Mantra, the most powerful and significant of all mantras.  It represents the Self which is the Supreme Non-dual Reality.  Bhur Bhuva Svaha denoting the three worlds are called the ‘Vyahrtis’. The Gayatri mantra commences with the words Tha'th Savithur Va'ray'nyam.

Mantras are given out by the Rishis, the ‘seers’ of the mantras. They are the men of wisdom who had realized the deep significance and the pregnant import of the mantras.  The Seer of the Gayatri Mantra is the Royal saint Visvamitra.  This mantra belongs to the Rig-Veda and it is found in the third Mandala, sixtieth Sutra, as the tenth Mantra.  It is also seen in the Shukla Yajur-Veda and the Krishna Yajur-Veda.

Every mantra has a presiding deity.  The belief is that when one chants a mantra, one is to do so keeping in one's mind the form of the deity.  In this way, just as one responds to being called by one's name, the Devata is invoked on the chanting of the mantra.  To facilitate this, we have a meditation stanza (Dhyana Sloka) that describes the Devata associated with the mantra.  The Gayatri Mantra is dedicated to the Lord Savitur, the Sun.

The Sun gives all illumination to the world; this prayer for light is naturally addressed to the ‘source of all light’ which, in the material world, is the Sun.  In the Gita, the Lord says that ‘the light that pervades the Sun and the Moon are all My Light.’  It follows that Savitur, the Lord of Gayatri, represents the Light of Consciousness, the Infinite, the Absolute.

This Mantra is never chanted for purposes of material gains, physical or otherwise.  Its very invocation concludes with an appeal to the Pure Consciousness to illumine our heart.  It is a prayer unto the Self, to unveil Itself and come to manifest as Pure Wisdom in our life.

This mantra is couched in the Vedic metre called Gayatri which is constituted of three lines of eight syllables each and is considered to be the most important mantra written in this metre.  By tradition, the Mantra itself has come to be known as Gayatri for this reason.  Etymologically, the word Gayatri means: 'the mantra which protects him who chants it' (Gaayantham thraa'ya'thay ithi gaayathri).

The usual prescribed daily worship (Sandhya karma) of a Hindu includes chanting of the Gayatri mantra.  The word sandhya means the blending point of day and night.  There are two Sandhyas in a day: early morning, when the east blushes with light and, in the evening, when the golden light fades into darkness.  The mid-day prayer (madhyaana) is perhaps a later introduction.

After getting up from the bed and answering the calls of nature, purify yourself completely.  With a steady mind, perform the morning japa, standing on your feet and facing East, till the sun rises above the horizon.  In the evening worship, do your japa sitting down and facing West until the stars emerge out.  The one who is chanting the mantra is to carry water in one's folded palm and at the end of each mantra-japa, offer it to the Lord.  This is known as Arghya pradhanam.

As this offering is made, the devotee says: `This Sun is Brahman' (Asaavaadhityo' Brahma), and performs Atma-Pradhakshana, turning round himself by his right.  This signifies that the devotee is ‘going round’ in reverence and devotion round the Lord Sun, the Brahman which is the Self in himself.

The Gayatri mantra is chanted generally at each Sandhya a minimum of ten times; however, a devotee may chant the mantra any number of times according to his faith and convenience, at any Sandhya.  But never is this mantra chanted at night; the rule is that Gayatri should not be chanted after sunset.

The disciple is initiated into the Gayatri mantra very early in life during a social ritual called the Upanayanam ceremony, presided over by the head of the family and the family-priest.  The word ‘Upa-nayanam’ means ‘bringing near’ – bringing the boy near a preceptor who initiates him by giving him the sacred mantra.  In Vedic literature, we find mention of the term Gayatri-Deeksha, meaning a discipline which one must undergo in order that one may become fit for taking part in any Vedic ritual.

The Vedic declarations glorify this initiation: "The father and mother have given birth to him from mutual desire, so that he is born from the womb; this his physical birth.  But the birth which is given through the Savitri (Gayatri) by the Preceptor who has mastered the Vedas is the true birth, the un-ageing and immortal."  After this initiation, the disciple is considered as twice-born (Dwija).

In ancient days, ladies used to chant Gayatri as freely as men; in those days, all ladies had their Upanayanam performed.  They used to learn the Vedas, teach the Vedas to others and chant the Gayatri mantra.  There are repeated declarations in Hindu sacred books that the effects of the Sadhana performed by men are their own, but the spiritual benefits acquired by the womenfolk are shared by their families.  Chinmayananda concludes from this:

“The Sastra injunctions lead us to the conclusion that women too can and should chant the Gayatri mantra regularly in their morning and evening worship.”

Of all the mantras, the most powerful and significant one is the single-syllabled incantation \ (OM), called the Pranava mantra.  It is accepted both as one with Brahman and as the medium, connecting man and God. Pranava means that which pervades life, or runs through Prana, the breath.

The Self is known in four states, of which the first three are the waking state, the dream stateand the deep-sleep state; these are represented in the three sounds of OM -- A, U and M.  The fourth state, the Turiya, is reflected in the silence that follows OM.

The waking state is superimposed on the A sound since it is the first state of consciousness; so is the sound A, the very first letter of the alphabet. The dream state occurs between the waking and the deep-sleep state, and is aptly represented by U since it is next to A in order of sounds.  M is the closing sound of the syllable, just as deep sleep is the final stage of the mind at rest. A short pregnant silence is inevitable between two successive OMs.  This is the state of perfect Bliss when the individual Self recognises its identity with the Supreme; this is the fourth state, the Turiya.

There must be some entity within ourselves which is present in the waking world, moves and illumines the dream, which is a distant observer in the deep-sleep world and yet is not conditioned by any of these three realms. This entity, conceived of as the fourth state (Turiya), is the Real, the Changeless, the Intelligent Principle.  While chanting OM, therefore, observing the silence between two OM japas is important.

OM represents the entire manifested world and the un-manifest, and also that which lies beyond both -- the Brahman, which is the changeless substratum for the changing objects of the world of experiences. Every mantra, therefore, is chanted after first chanting the pranava mantra OM.

The entire possibility of experience in life has been traced by the rishis into fourteen worlds: seven higher lokas and seven lower lokas. There are three worlds in which a limited ego-center comes to play its game of reincarnation and repeated deaths.  These are: the Bhur-loka, the physical earth, the Bhuvar-loka, the world next to the physical and closely connected with it but constituted of finer matter and the Suvar-loka, the heavenly world.  Beyond these are the four other worlds, wherein the ego comes to move about and enjoy in its higher evolutionary life, and they are called the Mahar-loka, Jana-loka, Tapa-loka and Satya-loka.  Below these seven worlds there is yet another set of seven lokas called the TALAAS: Paa'taalam, Mahaa'talam, Rasaa'talam, Talaa'talam, Su'talam, Vi'talam, and A'talam.  The etymological meaning of the word loka is "field of experience".

Of these fourteen worlds, or fields of experience, the "Bhur-Bhuvar-Suvar" are called the Vyaahritis.  In the Gayatri mantra when these Vyaahritis are chanted, the meditator can visualize the three worlds as arising from, existing in and disappearing into the Pranava AUM.  He can subjectively identify them with the waking, dream and deep-sleep states of consciousness, transcending which extends the realm of the Infinite. All of them are represented in OM.  In this sense, the Vyaahritis in the Gayatri (Bhur Bhuva Svaha) represent in one sweep, the entire world of the subjective and the objective experiences of man.

The Gayatri mantra is recognized as one of the oldest available divine hymns.  Inspite of the revolutionary changes that have taken place in our religious belief, this mantra continues to persist and has a compelling charm of its own to the millions of Hindu devotees.  It is believed and has also been actually observed, that through the chanting of this mantra with the right understanding of its sacred meaning, the ordinary negative tendencies in a human mind can be erased successfully.

The mantra's apparent meaning is:

"We meditate upon the auspicious godly light of the Lord Sun.  

May that heavenly light illumine the thought-flow in our intellect."  

It's deeper philosophic import is this:  

In our inner life, the Sun represents the Light-giver, the Illuminator of all experiences, the Atman.  It is around this Pure Consciousness in us, the inner center of our personality, that the matter envelopments (body, mind and intellect) function just as the entire solar system revolves around the sun, each planet at its appointed speed and each along its path.  By chanting the Gayathri mantra, the devotee invokes that pure consciousness in him to assist him in his efforts to get out of his state of Avidya so that it may illumine the intellect without being veiled by the cloud of his false knowledge.

Without the sun, life would be impossible; without the Atman, the matter-envelopments would be inert.  When this inner Sun-of-Life is appealed to for sending forth the brilliant rays of its radiance through the intellect, the devotee's prayer is that his intellect be steady without agitations and clean without the dirt of passions.  Thus, the prayer is:

May my perception of the world be clear

May my discrimination be subtle;

May my judgment be correct;

May my comprehension of situations and beings be precise and wise;

May all my perceptions be holistic and integral;

May my awareness become one with the Universal Consciousness.

OM Shanti: Shanti: Shanti:

Commentary by Swami Chinmayananda

On vyahruthis by Shriman Oppiliappan Sadagopan:

Here is my input on that important question on VyAhruthis , which has links to the sacred Manthram , the three Vedams  and PraNavam ultimately .

VyAhruthi: means utterance and in this case the utterance of a mystic word or words. Specifically, VYAhurthis are invoked during SandhyA Vandhanam. They are three in number (BhU:, Bhuva: and Suva:). Some account for 7 VyAhruthis. The number three fits nicely.

PoorvAchAryAs have explained that the Manthra dhrashtAs or the Rishis churned the 21 Rg Veda SaakhAs and obtained their essence in the form of 8 aksharams .These 8 letters are recognized as the essence of the  Rg Veda SaakhAs . Similar intensive efforts by the Rishis conversant with the Yajur and Saama Vedams led to the realization of 8 aksharams as the essence of Yajur Vedam and another set of 8 aksharams for the Saama Vedam .

Since Atharva Vedam is implicit in the other three Vedams, the Maharishis seemed to have stopped with the three Vedams alone. One can speculate whether the ChathurpAdha Gaayathri has the fourth paadham as the condensation of Atharva Vedam .

In total, there arose to prominence 24 aksharams with 8 each for the three VedAs. In these 24 aksharams, the essence of all the Vedams are contained / housed.

These 24 Aksharams together constitute the "ThripadhA  Gaayathri or AshtAkshara Gaayathri". Each of the 3 Paadhams of the most sacred Gaayathri Manthram is linked to one particular Vedam according to Manu. This manthram that protects those who recite it with the correct Svaram protects the reciter (Gaayantham ThrAyathee ithi Gaayathree). In view of Gaayathri manthram being the essence of the three VedAs, it is saluted as "ChandasAm MaathA".

Vaikunta Vaasi MukkUr Sri  Lakshmi NrusimhAcchAr Swamy goes on to explain that additional condensation of the 8 aksharams of each of the three VedAs (the three Paadhams of Gaayathree Manthram) gave rise to three sabdhams: BhU: , Bhuva: and Suva: . Together, the above three sabdhams joined to form the VyAhruthi manthram: "BhUr-Bhuva: Suva:".

Further churning of the three VyAhruthi manthrams led to additional compression /condensation: Out of BhU: came the letter "A". VyAhruthi Bhuva: gave rise to "U" and VyAhruthi Suva: led to "M" . When these three letters ( A, U, M) were United , one was blessed with PraNavam or EkAksharam. This could not be condensed any further.

MukkUr Swamy sums up the interrelationships this way: "All the VedAs are contained inside the Gaayathri manthram; Gaayathri is housed inside the VyAhruthis; The VyAhruthis are contained inside PraNavam, which has all the Veda manthrams inside it. PraNavam is saluted as "Veda Siras or Veda ChoodAmaNi".

The detailed esoteric meanings of PraNavam is covered by Swamy Desikan in the Moola ManthrAdhikAram of Srimath Rahasya Thraya Saaram .

Additional comments on VyAhruthis

Rg Veda Manthram (X.33.5) gives a clue to these three VyAhruthis:

Yasya maa harithO raTE THISRO  vahanthi saadhuyaa sthavai sahasradakshiNE

(Meaning) : " I praise Him at the ceremony, where three vital energies, yoked in the chariot of body , carry us nicely forward to the place of work or worship, in which He presents to us with thousands of rewards".

The three vital energies can be viewed as the three VyAhruthIs condensing to form the most important PraNavam .