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 Gayatri. And if a man were to receive as his fee everything as far as this threefold knowledge extends, he would obtain that second foot of the Gayatri. And if a man were to receive as his fee everything whatsoever breathes, he would obtain that third foot of the Gayatri. But 'that fourth bright foot, shining high above the skies' cannot be obtained by anybody—whence then could one receive such a fee?

In plain words: Even if a teacher were paid with the three worlds, all the knowledge of the Vedas (the holy scriptures), and every living thing, that would only equal the first three parts of the Gayatri prayer. Its fourth, shining part is beyond anything anyone can own, so no payment could ever match it.