Brihadaranyaka-Upanishad: Fifth Adhyâya, Fourteenth Brahmana
1. The words Bhumi (earth), Antariksha (sky), and Dyu (heaven) form eight syllables. One foot of the Gâyatrî consists of eight syllables. This (one foot) of it is that (i.e. the three worlds). And he who thus knows that foot of it, conquers as far as the three worlds extend.
2. The Rikas, the Yagumshi, and the Samani form eight syllables. One foot (the second) of the Gâyatrî consists of eight syllables. This (one foot) of it is that (i.e. the three Vedas, the Rig-veda, Yagur-veda, andsama-veda). And he who thus knows that foot of it, conquers as far as that threefold knowledge extends.
3. The Prâna (the up-breathing), the Apana (the down-breathing), and the Vyana (the back-breathing) form eight syllables. One foot (the third) of the Gâyatrî consists of eight syllables. This (one foot) of it is that (i.e. the three vital breaths). And he who thus knows that foot of it, conquers as far as there is anything that breathes. And of that (Gâyatrî, or speech) this indeed is the fourth (turiya), the bright (darsata) foot, shining high above the skies. What is here called turiya (the fourth) is meant for katurtha (the fourth); what is called darsatam padam (the bright foot) is meant for him who is as it were seen (the person in the sun); and what is called paroragas (he who shines high above the skies) is meant for him who shines higher and higher above every sky. And he who thus knows that foot of the Gâyatrî, shines thus himself also with happiness and glory.
4. That Gâyatrî (as described before with its three feet) rests on that fourth foot, the bright one, high above the sky. And that again rests on the True (satyam), and the True is the eye, for the eye is (known to be) true. And therefore even now, if two persons come disputing, the one saying, I saw, the other, I heard, then we should trust the one who says, I saw. And the True again rests on force (balam), and force is life (prâna), and that (the True) rests on life. Therefore they say, force is stronger than the True. Thus does that Gâyatrî rest with respect to the self (as life). That Gâyatrî protects (tatre) the vital breaths (gayas); the gayas are the prânas (vital breaths), and it protects them. And because it protects (tatre) the vital breaths (gayas), therefore it is called Gâyatrî. And that Savitri verse which the teacher teaches, that is it (the life, the prâna, and indirectly the Gâyatrî); and whomsoever he teaches, he protects his vital breaths.
5. Some teach that Savitri as an Anushtubh verse, saying that speech is Anushtubh, and that we teach that speech. Let no one do this, but let him teach the Gâyatrî as Savitri. And even if one who knows this receives what seems to be much as his reward (as a teacher), yet this is not equal to one foot of the Gâyatrî.
6. If a man (a teacher) were to receive as his fee these three worlds full of all things, he would obtain that first foot of the Gâyatrî. And if a man were to receive as his fee everything as far as this threefold knowledg,e extends, he would obtain that second foot Of the Gâyatrî. And if a man were to receive as his fee everything whatsoever breathes, he would obtain that third foot of the Gâyatrî. But that fourth bright foot, shining high above the skies, cannot be obtained by anybody—whence then could one receive such a fee?
7. The adoration of that (Gâyatrî):
“O Gâyatrî, thou hast one foot, two feet, three feet, four feet. Thou art footless, for thou art not known. Worship to thy fourth bright foot above the skies.” If one (who knows this) hates some one and says, “May he not obtain this,” or “May this wish not be accomplished to him,”then that wish is not accomplished to him against whom he thus prays, or if he says, “May I obtain this.”
8. And thus Ganaka Vaideha spoke on this point to Budila Asvatarasvi: “How is it that thou who spokest thus as knowing the Gâyatrî, hast become an elephant and carriest me?” He answered: “Your Majesty, I did not know its mouth. Agni, fire, is indeed its mouth; and if people pile even what seems much (wood) on the fire, it consumes it all. And thus a man who knows this, even if he commits what seems much evil, consumes it all and becomes pure, clean, and free from decay and death.”