The Vedanta Sutras, commentary by Sankaracharya (SBE34), tr. by George Thibaut  at sacred-texts.com
23. And on account of its form being mentioned.
Subsequently to the passage, 'Higher than the high Imperishable,' we meet (in the passage, 'From him is born breath,' &c.) with a description of the creation of all things, from breath down to earth, and then with a statement of the form of this same source of beings as consisting of all created beings, 'Fire is his head, his eyes the sun and the moon, the quarters his ears, his speech the Vedas disclosed, the wind his breath, his heart the universe; from his feet came the earth; he is indeed the inner Self of all things.' This statement of form can refer only to the
highest Lord, and not either to the embodied soul, which, on account of its small power, cannot be the cause of all effects, or to the pradhâna, which cannot be the inner Self of all beings. We therefore conclude that the source of all beings is the highest Lord, not either of the other two.--But wherefrom do you conclude that the quoted declaration of form refers to the source of all beings?--From the general topic, we reply. The word 'he' (in the clause, 'He is indeed the inner Self of all things') connects the passage with the general topic. As the source of all beings constitutes the general topic, the whole passage, from 'From him is born breath,' up to, 'He is the inner Self of all beings,' refers to that same source. Similarly, when in ordinary conversation a certain teacher forms the general topic of the talk, the phrase, 'Study under him; he knows the Veda and the Vedângas thoroughly,' as a matter of course, refers to that same teacher.--But how can a bodily form be ascribed to the source of all beings which is characterised by invisibility and similar attributes?--The statement as to its nature, we reply, is made for the purpose of showing that the source of all beings is the Self of all beings, not of showing that it is of a bodily nature. The case is analogous to such passages as, 'I am food, I am food, I am the eater of food' (Taitt. Up. III, 10, 6).--Others, however, are of opinion 1 that the statement quoted does not refer to the source of all beings, because that to which it refers is spoken of as something produced. For, on the one hand, the immediately preceding passage ('From him is born health, mind, and all organs of sense, ether, air, light, water, and the earth, the support of all') speaks of the aggregate of beings from air down to earth as something produced, and, on the other
hand, a passage met with later on ('From him comes Agni, the sun being his fuel,' up to 'All herbs and juices') expresses itself to the same purpose. How then should all at once, in the midst of these two passages (which refer to the creation), a statement be made about the nature of the source of all beings?--The attribute of being the Self of all beings, (which above was said to be mentioned in the passage about the creation, 'Fire is his head,' &c., is not mentioned there but) is stated only later on in a passage subsequent to that which refers to the creation, viz. 'The Person is all this, sacrifice,' &c. (II, 1, 10).--Now, we see that sruti as well as smriti speaks of the birth of Pragâpati, whose body is this threefold world; compare Rig-veda Samh. X, 121, 1, 'Hiranyagarbha arose in the beginning; he was the one born Lord of things existing. He established the earth and this sky; to what God shall we offer our oblation?' where the expression 'arose' means 'he was born.' And in smriti we read, 'He is the first embodied one, he is called the Person; as the primal creator of the beings Brahman was evolved in the beginning.' This Person which is (not the original Brahman but) an effect (like other created beings) may be called the internal Self of all beings (as it is called in II, 1, 4), because in the form of the Self of breath it abides in the Selfs of all beings.--On this latter explanation (according to which the passage, 'Fire is his head,' &c., does not describe the nature of the highest Lord, and can therefore not be referred to in the Sûtra) the declaration as to the Lord being the 'nature' of all which is contained in the passage, 'The Person is all this, sacrifice,' &c., must be taken as the reason for establishing the highest Lord, (i.e. as the passage which, according to the Sûtra, proves that the source of all beings is the highest Lord 1.)
141:1 Vrittikridvyâkhyâm dûshayati, Go. Ân.; ekadesinam dûshayati, Ânanda Giri; tad etat paramatenâkshepasamâdhânâbhyâm vyâkhyâya svamatena vyâkashte, punah sabdo#pi pûrvasmâd visesham dyotayann asyeshtatâm sûkayati, Bhâmatî.--The statement of the two former commentators must be understood to mean--in agreement with the Bhâmatî--that Sankara is now going to refute the preceding explanation by the statement of his own view. Thus Go. Ân. later on explains 'asmin pakshe' by 'svapakshe.'
142:1 The question is to what passage the 'rûpopanyâsât' of the Sûtra refers.--According to the opinion set forth first it refers to Mu. Up. II, 1, 4 ff.--But, according to the second view, II, 1, 4 to II, 1, 9, cannot refer to the source of all beings, i.e. the highest Self, because that entire passage describes the creation, the inner Self of which is not the highest Self but Pragâpati, i.e. the Hiranyagarbha or Sûtrâtman of the later Vedânta, who is himself an p. 143 'effect,' and who is called the inner Self, because he is the breath of life (prâna) in everything.--Hence the Sûtra must be connected with another passage, and that passage is found in II, 1, 10, where it is said that the Person (i.e. the highest Self) is all this, &c.