The word has power even the ordinary written word has a power. If it is an inspired word it has still more power. What kind of power or power for what depends on the nature of the inspiration and the theme and the part of the being it touches. If it is the Word itself, as in certain utterances of the great Scriptures, Vedas, Upanishads, Gita, it may well have a power to awaken a spiritual and uplifting impulse, even certain kinds of realization. To say that it cannot contradicts spiritual experience. The Vedic poets regarded their poetry as Mantras, they were the vehicles of their own realizations and could become vehicles of realization for others. Naturally, these mostly would be illuminations, not the settled and permanent realization that is the goal of Yoga but they could be steps on the way or at least lights on the way. l have had in former times many illuminations. even initial realisations while meditating on verses of the Upanishads or the Gita. Anything that carries the Word, the Light in it, spoken or written, can light this fire within, open a sky. as it were. bring the effective vision of which the Word is the body. The Gita owes its poetical success to its starting from a great and critical situation in life, having that in view and always returning upon it, and to its method which is to seize on a spiritual experience or moment or stage of the inner life and throw it into the form of thought; and this. though a delicate operation, can keep well within the limits of the poetic manner of speech. only where it overburdens itself with metaphysical matter and deviates into sheer philosophic definition and discrimination. which happens essentially in two or three of its closing chapters, does the poetic voice sink under the weight, even occasionally into fiattest versified prose. The mantra as l have tried to describe it in The Future Poetry is a word of power and light and comes from the Overmind inspiration or from some very high plane of lntuition. Its characteristics are a language that conveys infinitely more than the mere surface sense of the words seems to indicate. a rhythm that means even more than the language and is born out of the Infinite and disappears into it, and the power to convey not merely the mental, vital or physical contents or indications or values of the thing uttered, but its significance and figure in some fundamental and original consciousness which is behind all these and greater. The passages you mention from the Upanishad and the Gita have certainly the Overmind accent.
WritingThe Delight of Krishna
Gita: A Poetry of Overmind Inspiration
Sri Aurobindo