GAYATRI MANTRA

                                                     The Gāyatrī Mantra is a highly revered mantra, based on a Vedic Sanskrit verse from a hymn of the Rigveda (3.62.10), attributed to the rishi Viśvāmitra. The mantra is named for its vedic gāyatrī metre. As the verse invokes the deva Savitr, it is also called Sāvitrī. Its recitation is traditionally preceded by oṃ and the formula bhūr bhuvaḥ svaḥ, known as the mahāvyāhṛti ("great utterance").

The Gayatri Mantra is repeated and cited very widely in vedic literature, and praised in several well-known classical Hindu texts such as Manusmṛti, Harivamsa, and the Bhagavad Gita. The mantra is an important part of the upanayanam ceremony for young males in Hinduism, and has long been recited by Brahmin males as part of their daily rituals. Modern Hindu reform movements spread the practice of the mantra to include women and all castes and its use is now very widespread.

Text

Recitation of the Gayatri Mantra is preceded by oṃ(ॐ) and the formula bhūr bhuvaḥ svaḥ (भूर् भुवः स्वः), known as the mahāvyāhṛti ("great utterance"). This prefixing of the mantra proper is described in the Taittiriya Aranyaka (2.11.1-8), which states that scriptural recitation was always to begin with the chanting of the syllable oṃ, followed by the three Vyahrtis and the Gayatri verse.
Following the mahāvyāhṛti is then the mantra proper, the verse RV 3.62.10:

In Devanagari: तत् सवितुर्वरेण्यं । भर्गो देवस्य धीमहि । धियो यो नः प्रचोदयात् ॥

In IAST: tát savitúr váreṇyaṃ bhárgo devásya dhīmahi dhíyo yó naḥ pracodáyāt

Whereas in principle the gāyatrī metre specifies three pādas of eight syllables each, the text of the verse as preserved in the Rigveda Samhita is one syllable short, the first pāda counting seven instead of eight. Metrical restoration would emend the attested vareṇyaṃ with a tetra-syllabic vareṇiyaṃ

Brahmanical usage

                     In traditional Brahmin practice the Gayatri Mantra is addressed to God as the divine life-giver, symbolized by Savitr (the sun), and is most often recited at sunrise and sunset. It is believed by practitioners that reciting the mantra bestows wisdom and enlightenment, through the vehicle of the Sun (Savitr), who represents the source and inspiration of the universe. Recitation at sunrise every morning is part of the daily ritual. While often associated with outward ritual offerings, it can be recited more inwardly and without rites, a practice generally known as japa.
Imparting the Sāvitrī mantra to young Hindu males is an important part of the traditional upanayanam ceremony, which marks the beginning of study of the Vedas. S. Radhakrishnan has described this as the essence of the ceremony, which is sometimes called "Gayatri diksha", i.e. initiation into the Gayatri Mantra. However, traditionally, the stanza RV.3.62.10 is the Sāvitrī imparted only to Brahmin boys. Other Sāvitrī verses are used in the upanayanam ceremony for non-Brahmins: RV.1.35.2, in the Trishtubh meter, for a Kshatriya; and, either RV.1.35.9 or RV.4.40.5, in the Jagati meter, for a Vaishya.
                            

Brahmoism

In 1827 Ram Mohun Roy published a dissertation on the Gayatri Mantra that analysed it in the context of various Upanishads. Roy prescribed a Brahmin to always pronounce Om at the beginning and end of the Gayatri Mantra. From 1830, the Gayatri Mantra was used for private devotion of Brahmos. In 1843, the First Covenant of Brahmo Samaj required Gayatri Mantra for Divine Worship. From 1848-1850 with the rejection of Vedas, the Adi Dharm Brahmins use Gayatri Mantra in their private devotions.

Hindu revivalism

In the later 19th century, Hindu reform movements extended the chanting of the Gayatri Mantra beyond caste and gender limitations. In 1898, Swami Vivekananda began initiating non-Brahmins with the sacred thread ceremony and the Gayatri Mantra. He based this on the interpretations of the Vedas and Bhagavad Gita that Brahmin status is earned and not hereditary.The Arya Samaj notably spread the teaching that recitation of the mantra was not limited to males, but that women could rightfully be taught both the Vedas and the Gayatri Mantra. In his writings, S. Radhakrishnan encouraged the teaching of Gayatri  mantra to men and women of all castes.