The gāyatrī mantra is probably the most widely known and most recited mantra in the world. It originally appears in the ṛgveda, book 3, chapter 62, verse 10:
धियो यो नः प्रचोदयात्
dhiyo yo naḥ pracodayāt
Savitṛ, the most excellent and resplendent Rising Sun, we meditate upon you. Grant us the highest inspiration in our efforts.
The mantra is dedicated to Savitṛ, the god of the rising sun (after rising, the sun is called Sūrya), and is therefore also known as the sāvitrī mantra.
The word gāyatrī has several meanings: it is the name of the famous vedic mantra, it is the poetic meter that the mantra is written in (consisting of 24 syllables, three lines of eight syllables each), and it is the name of the goddess who revealed the mantra to the sage Viśvāmitra. The word itself literally means “song of three” (gāya, “song” + tra, “three”), which itself has a double meaning: it can refer to the three lines of the mantra (and all mantras composed in the same meter), as well as to the goddess’s nature as being the combined essences of tridevī: Mahāsarasvatī, Mahālakṣmī, and Mahākālī (the respective consorts, or śaktis, of the Hindu trinity of Brahmā, Viṣṇu, and Śiva). Being the combination of these three śaktis, Gāyatrī is also considered Ādi Parāśakti, the supreme primordial energy.
The mantra is often preceded by the so called mahāvyāhṛti, the “great declaration”:
ॐ भूः ॐ भुवः ॐ स्वः ॐ महः
ॐ जनः ॐ तपः ॐ सत्यं
धियो यो नः प्रचोदयात्
oṃ bhūḥ oṃ bhuvaḥ oṃ svaḥ oṃ mahaḥ
oṃ janaḥ oṃ tapaḥ oṃ satyaṃ
dhiyo yo naḥ pracodayāt
The mahāvyāhṛti is a declaration of the names of the seven spiritual realms (lokāḥ) including and above earth. These lokāḥ are: bhūrloka (our realm, earth), bhuvarloka (realm of lower demigods and ghosts), svarloka (heaven, realm of the devas), maharloka (realm of Bhṛgu and other mahāṛṣis), janaloka (realm of Sanatkumāra and the other divine sons of Brahmā), tapoloka (the abode of Lord Brahmā and various highly advanced souls), and satyaloka (the realm of those who are completely free from the cycle of rebirth). The gāyatrī mantra is most often recited with just the first three of these, known as the vyāhṛtitraya, or the “three-fold declaration” of “oṃ bhūrbhuvaḥ svaḥ”.
According to the Manusmṛti — the “Laws of Manu”, one of the most important treatises on dharma, the spiritual duties of the both the individual and society at large — reciting the gāyatrī mantra, preceded by the vyāhṛtitraya, will lead one to brahman, the Supreme Spirit.
ओङ्कारपूर्विकास्तिस्रो महाव्याहृतयोऽव्ययाः ।
त्रिपदा चैव सावित्री विज्ञेयं ब्रह्मणो मुखम् ॥
oṅkārapūrvikāstisro mahāvyāhṛtayo'vyayāḥ ।
tripadā caiva sāvitrī vijñeyaṃ brahmaṇo mukham ॥
The syllable “oṃ” followed by the imperishable three-fold great declaration (“bhūrbhuvaḥ svaḥ”), then the three-lined sāvitrī (gāyatrī mantra), shall be known as the “Mouth of Brahman”.
Another treatise on dharma called Vasiṣṭha Dharmasutra recommends reciting the gāyatrī mantra with all seven of the vyāhṛtis:
प्रणवे नित्ययुक्तस्स्याद् व्याहृतीषु च सप्तसु ।
त्रिपदायां च गायत्र्यां न भयं विद्यते क्वचित् ॥
praṇave nityayuktassyād vyāhṛtīṣu ca saptasu ।
tripadāyāṃ ca gāyatryāṃ na bhayaṃ vidyate kvacit ॥
One who is constantly engaged in reciting “oṃ”, the seven vyāhṛtis, and the three-lined gāyatrī mantra shall fear no danger anywhere.
So why worship the sun? In the time of the ṛgveda, the sun was considered a visible manifestation of parabrahman, the Supreme Spirit, and was called pratyakṣa devatā, the divinity before our eyes. The sun is the source of all the light and heat that sustains life in our world, so it is only natural that it should be worshipped as a visible stand-in for invisible Spirit.
Reciting the mahāvyāhṛti or the vyāhṛtitraya along with the gāyatrī mantra is an asseveration that parabrahman, the Supreme Spirit metaphorized as our physical sun, is the selfsame divine light shining on all physical, astral, and causal lokāḥ simultaneously1.
There are two main models in the vedas and purāṇas for the layout of the created universe(s). The first, called trailokya, describes three spheres: earth (pṛthivī), sky (antarikṣa), and heaven (dyu).
The second model describes fourteen worlds, with seven below the earth and six above. In this model, the earth (pṛthivī) is called bhūloka, sky (antarikṣa) is called bhuvarloka, and heaven (dyu) is called svarloka.
Reciting the vyāhṛtitraya (as opposed to the full mahāvyāhṛti) is done according to the trailokya model of creation, where the three possible realms are “earth”, “sky”, and “heaven”. Another very common phrasing for these three realms is “physical”, “astral”, and “causal”. Some interpret the vyāhṛtitraya as meaning the physical, astral, and causal worlds on which the divine light of the sun shines. Others interpret it as the physical, astral, and causal bodies surrounding the atman (individualized soul), and the sun worshipped with the mantra is the light of divinity within us all. ↩