गोविन्द भाष्य (श्रील बलदेव विद्याभूषण - अचिन्त्यभेदाभेद वेदान्त ब्रह्मसूत्र भाष्य सटीक)

mention the creation of ether. In the previously quoted passage of Chāndogya
Upaniṣad the creation of fire, water, and grains is mentioned. However there is no
mention of the creation of ether. For this reason ether must not have been created.
That is the meaning.
This idea is refuted in the following sūtra:
Sūtra 2
asti tu
asti—is; tu—indeed.
Indeed it is so.
Purport by Śrīla Baladeva Vidyābhūṣaṇa
The word "tu" (indeed) is used here to remove doubt. The word "asti" (it is so)
means, "It is so that ether was created." Although the creation of ether is not
described in the Chāndogya Upaniṣad, it is described in the Taittirīya Upaniṣad in
the following words:
tasmād vā etasmād ātmana ākāśaḥ sambhūtaḥ ākāśād vāyur vāyor agnir agner āpo
ābhyo mahatī pṛthivī
"From the Supreme Personality of Godhead, ether was manifested. From ether,
air was manifested. From air, fire was manifested. From fire, water was manifested.
From water, earth was manifested."
Another doubt is expressed in the next sūtra.
Sūtra 3
gauṇy asambhavāc chabdāc ca
gauṇī—figure of speech; asambhavāt—because of being impossible; śabdāt—
because of scripture; ca—also.