The Vedanta Sutras of Badarayana, Commentary by Sankara (SBE38), tr. by George Thibaut [1896] at sacred-texts.com
10. Fire (is produced) thence (i.e. from air); for thus (the text) declares.
In the Khândogya it is said that fire has for its source that which is (Brahman), in the Taittirîyaka that it has the air for its source. There being thus a conflict of scriptural passages with regard to the origin of fire, the pûrvapakshin maintains that fire has Brahman for its source.--Why?--Because the text, after having stated at the outset that there existed only that which is, teaches that it sent forth fire; and because the assertion of everything being known through Brahman is possible only in case of everything;
being produced from Brahman; and because the scriptural statement as to the 'Taggalân' (Kh. Up. III, 14, 1) specifies no difference 1; and because another scriptural passage (Mu. Up. II, 1, 3) teaches that everything without exception is born from Brahman. The Taittirîyaka also makes a statement about the entire world without any exception, 'after having brooded he sent forth all whatever there is' (Taitt. Up. II, 6). Hence the statement that 'fire was produced from air' (Taitt. Up. II, 1) must be considered to teach the order of succession only 'fire was produced subsequently to air.'
To this the Sûtra replies that fire was produced thence, i.e. from air, because the text declares it to be so--'from air sprang fire.' For if fire had sprung directly from Brahman and not from air, the scriptural statement that 'fire sprang from air' would be contradicted thereby. That that statement should intimate the order of succession merely, as maintained by the pûrvapakshin, we cannot admit. For as in the preceding sentence ('from that Self sprang ether') the fifth case (âtmanah) denotes the Self as that from which the origination proceeds, and as the same verb sprang') governs our sentence also, and as in the following sentences also--such as 'from earth the herbs'--the fifth case (prithivyâh) denotes that from which something proceeds we understand that in our sentence also the fifth case (vâyoh) denotes that from which fire proceeds. Moreover, if we should explain our sentence to mean 'after air fire was produced,' we should have to supply some preposition (or adverb as 'after,' 'subsequently'), while that construction which rests on the proper sense of the fifth case-affix is ready made at hand and does not require anything to be applied. The passage therefore intimates that fire springs from air.--But, it may be said, the other scriptural passage ('sent forth fire') intimates that fire springs from Brahman. Not so, we reply; for this latter passage remains uncontradicted, even if we assume that fire sprang from Brahman only through intermediate links (not directly).
Even the supposition that Brahman, after having created ether and air, assumed the form of air and thus created fire would not be opposed to fire having sprung from Brahman; for we may say equally that milk comes from the cow, that curds come from the cow, that cheese comes from the cow. There is, moreover, a scriptural passage declaring that Brahman abides as the Self of its effects, viz. Taitt Up. II, 7, 'That made itself its Self.' And analogously Smriti--in the passage beginning 'Cognition, knowledge, steadiness of mind' (Bha. Gî. X, 4)--says about the Lord, 'From me only spring the manifold states of the beings.' For although cognition and so on are observed to spring directly from their immediate causes, yet (the assertion made in the passage quoted holds good), since the entire aggregate of beings is, directly or indirectly, derived from the Lord.--Thereby those scriptural passages are accounted for which speak of the creation (on the whole) without specifying the order of succession 1; for they may be explained anyhow, while on the other hand the passages specifying the order of creation cannot be turned in any other way (i.e. not away from their direct sense). The general assertion, moreover, of everything springing from Brahman requires only that all things should ultimately proceed from that which is, not that they should be its immediate effects.--Thus there remains no difficulty.
21:1 But implies the whole world to have sprung from Brahman.
22:1 I.e. it appears from the preceding discussion that those passages have to be explained in such a way as to agree with those other passages which state the order of the created beings.