24. The word “light” refers to Brahman on account of the mention of feet in a connected passage.
The Upanishad speaks of that light which shines above heaven and enjoins meditation upon it. The question is whether this refers to physical light or Brahman.
The sutra establishes that it is Brahman, because a preceding passage describes the cosmic Purusha whose one foot is all beings and whose remaining three feet are immortal in heaven. The later reference to light connected with heaven therefore continues the same Brahman-topic.
25. If it is objected that the passage refers only to the Gayatri metre because it is mentioned earlier, this is not so.
The metre serves as a means for fixing the mind upon Brahman. One meditates not on syllables alone, but on Brahman as connected with the Gayatri.
This interpretation agrees with the surrounding passages in which Brahman is clearly the chief topic.
26. The representation of beings, earth, body, and heart as the feet is possible only when Brahman is intended.
These cannot meaningfully be the feet of a mere metrical arrangement. Therefore Gayatri here signifies Brahman as associated with the metre.
This same Brahman is recognised again as “light” in the later passage.
27. If it is said that the Brahman in the Gayatri passage cannot be the same as the Brahman in the light passage because of a difference in specification, this objection does not stand.
There is no contradiction in saying that Brahman is in heaven in one place and above heaven in another. Both descriptions can refer to the same transcendent reality from different contemplative standpoints.
Therefore the word “light” is to be understood as Brahman.