The Vedanta Sutras, commentary by Sankaracharya (SBE34), tr. by George Thibaut  at sacred-texts.com
REVERENCE TO THE HIGHEST SELF!
1. The abode of heaven, earth, and so on (is Brahman), on account of the term 'own,' i.e. Self.
We read (Mu. Up. II, 2, 5), 'He in whom the heaven, the earth, and the sky are woven, the mind also with all the vital airs, know him alone as the Self, and leave off other words! He is the bridge of the Immortal.'--Here the doubt arises whether the abode which is intimated by the statement of the heaven and so on being woven in it is the highest Brahman or something else.
The pûrvapakshin maintains that the abode is something else, on account of the expression, 'It is the bridge of the Immortal.' For, he says, it is known from every-day experience that a bridge presupposes some further bank to which it leads, while it is impossible to assume something further beyond the highest Brahman, which in Scripture is called 'endless, without a further shore' (Bri. Up. II, 4, 12). Now if the abode is supposed to be something different from Brahman, it must be supposed to be either the pradhâna known from Smriti, which, as being the (general) cause, may be called the (general) abode; or the air known from Sruti, of which it is said (Bri. Up. III, 7, 2, 'Air is that thread, O Gautama. By air as by a thread, O Gautama, this world and the other world and all beings are strung together'), that it supports all things; or else the embodied soul which, as being the enjoyer, may be considered as an abode with reference to the objects of its fruition.
Against this view we argue with the sûtrakâra as follows:--'Of the world consisting of heaven, earth, and so on, which in the quoted passage is spoken of as woven (upon something), the highest Brahman must be the abode.'--Why?--On account of the word 'own,' i.e. on account of the word 'Self.' For we meet with the word 'Self' in the passage, 'Know him alone as the Self.' This term 'Self' is
thoroughly appropriate only if we understand the highest Self and not anything else.--(To propound another interpretation of the phrase 'svasabdât' employed in the Sûtra.) Sometimes also Brahman is spoken of in Sruti as the general abode by its own terms (i.e. by terms properly designating Brahman), as, for instance (Kh. Up. VI. 8, 4), 'All these creatures, my dear, have their root in the being, their abode in the being, their rest in the being 1.'--(Or else we have to explain 'svasabdena' as follows), In the passages preceding and following the passage under discussion Brahman is glorified with its own names 2; cp. Mu. Up. II, 1, 10, 'The Person is all this, sacrifice, penance, Brahman, the highest Immortal,' and II, 2, 11, 'That immortal Brahman is before, is behind, Brahman is to the right and left.' Here, on account of mention being made of an abode and that which abides, and on account of the co-ordination expressed in the passage, 'Brahman is all' (Mu. Up. II, 2, 11), a suspicion might arise that Brahman is of a manifold variegated nature, just as in the case of a tree consisting of different parts we distinguish branches, stem, and root. In order to remove this suspicion the text declares (in the passage under discussion), 'Know him alone as the Self.' The sense of which is: The Self is not to be known as manifold, qualified by the universe of effects; you are rather to dissolve by true knowledge the universe of effects, which is the mere product of Nescience, and to know that one Self, which is the general abode, as uniform. Just as when somebody says, 'Bring that on which Devadatta sits,' the person addressed brings the chair only (the abode of Devadatta), not Devadatta himself; so the passage, 'Know him alone as the Self,' teaches that the object to be known is the one uniform Self which constitutes the general abode. Similarly another scriptural passage reproves him who believes in the unreal world of effects,
[paragraph continues] 'From death to death goes he who sees any difference here'(Ka. Up. II, 4, 11). The statement of co-ordination made in the clause 'All is Brahman' aims at dissolving (the wrong conception of the reality of) the world, and not in any way at intimating that Brahman is multiform in nature 1; for the uniformity (of Brahman's nature) is expressly stated in other passages such as the following one, 'As a mass of salt has neither inside nor outside, but is altogether a mass of taste, thus indeed has that Self neither inside nor outside, but is altogether a mass of knowledge' (Bri. Up. IV, 5, 13).--For all these reasons the abode of heaven, earth, &c. is the highest Brahman.--Against the objection that on account of the text speaking of a 'bridge,' and a bridge requiring a further bank, we have to understand by the abode of heaven and earth something different from Brahman, we remark that the word 'bridge' is meant to intimate only that that which is called a bridge supports, not that it has a further bank. We need not assume by any means that the bridge meant is like an ordinary bridge made of clay and wood. For as the word setu (bridge) is derived from the root si, which means 'to bind,' the idea of holding together, supporting is rather implied in it than the idea of being connected with something beyond (a further bank).
According to the opinion of another (commentator) the word 'bridge' does not glorify the abode of heaven, earth, &c., but rather the knowledge of the Self which is glorified in the preceding clause, 'Know him alone as the Self,' and the abandonment of speech advised in the clause, 'leave off other words;' to them, as being the means of obtaining immortality, the expression 'the bridge of the immortal' applies 2. On that account we have to set aside the assertion that, on account of the word 'bridge,' something different from Brahman is to be understood by the abode of heaven, earth, and so on.
155:1 From passages of which nature we may infer that in the passage under discussion also the 'abode' is Brahman.
155:2 From which circumstance we may conclude that the passage under discussion also refers to Brahman.
156:1 Yat sarvam avidyâropitam tat sarvam paramârthato brahma na tu yad brahma tat sarvam ity arthah. Bhâmatî.
156:2 So that the passage would have to be translated, 'That, viz. knowledge, &c. is the bridge of the Immortal.'