"Om Bhur Buvaha Swaha Tatsaviturvareñyam Bhargo Devasya Dhimahi, Dhiyo Yonaha Pracodayat”
Brahmarshi Vishvamitra (Sanskrit विश्वामित्र viśvā-mitra "all-friend") is one of the most venerated rishi's or sages of ancient times in India. He is also credited as the author of most of Mandala 3 of the Rigveda, including the revered great Gayatri Mantra. It is a mantra cum prayer and is found in all the three Vedas; Rig, Yajur and Sama Veda. Veda's clearly state that anyone can chant this Mantra, and gain its benefits. The Puranas mention that only 24 Rishis since antiquity have understood the whole meaning of, and thus wielded the whole power of, the Gayatri Mantra. Sage Vishvamitra is supposed to be the first and Sage Yajnavalkya the last.
Gayatri is said to be the Mother (origin) of the Vedas. The scriptures describe that the commentary of the four segments of the Gayatri Mantra through the four mouths of Lord Brahma has been compiled into four Vedas as indicated below:
The segment of Gayatri Mantra and the Veda generated from it
Om Bhur Bhuvah Swaha - The Rig Veda
Tatsaviturvarenyam - The Yajur Veda
Bhargo evasya Dhimahi - The Sama Veda
Dhiyo Yonah Pracodayat - The Atharva Veda:
If man could ever attain long-lasting peace and happiness, it will be possible only through Gayatri mantra. Now I am telling you a story, how a King who was relieved of his sickness by a Brahmin with his Gayathri manthra. At least, we must chant Gayathri manthra for twelve times a day to attain long-lasting peace and happiness.