The Vedanta Sutras, commentary by Sankaracharya (SBE34), tr. by George Thibaut  at sacred-texts.com
REVERENCE TO THE HIGHEST SELF!
In the first pâda Brahman has been shown to be the cause of the origin, subsistence, and reabsorption of the entire world, comprising the ether and the other elements. Moreover, of this Brahman, which is the cause of the entire world, certain qualities have (implicitly) been declared, such as all-pervadingness, eternity, omniscience, its being the Self of all, and so on. Further, by producing reasons showing that some words which are generally used in a different sense denote Brahman also, we have been able to determine that some passages about whose sense doubts are entertained refer to Brahman. Now certain other passages present themselves which because containing only obscure indications of Brahman give rise to the doubt whether they refer to the highest Self or to something else. We therefore begin the second and third pâdas in order to settle those doubtful points.
1. (That which consists of mind is Brahman) because there is taught what is known from everywhere.
Scripture says, 'All this indeed is Brahman, beginning, ending, and breathing in it; thus knowing let a man meditate with calm mind. Now man is made of determination (kratu); according to what his determination is in this world so will he be when he has departed this life. Let him therefore form this determination: he who consists of mind, whose body is breath (the subtle body),' &c. (Kh. Up. III, 14). Concerning this passage the doubt presents itself whether what is pointed out as the object of meditation, by means of attributes such as consisting of mind, &c., is the embodied (individual) soul or the highest Brahman.
The embodied Self, the pûrvapakshin says.--Why?--Because the embodied Self as the ruler of the organs of action is well known to be connected with the mind and so on, while the highest Brahman is not, as is declared in several scriptural passages, so, for instance (Mu. Up. II, 1, 2),
[paragraph continues] 'He is without breath, without mind, pure.'--But, it may be objected, the passage, 'All this indeed is Brahman,' mentions Brahman directly; how then can you suppose that the embodied Self forms the object of meditation?--This objection does not apply, the pûrvapakshin rejoins, because the passage does not aim at enjoining meditation on Brahman, but rather at enjoining calmness of mind, the sense being: because Brahman is all this, taggalân, let a man meditate with a calm mind. That is to say: because all this aggregate of effects is Brahman only, springing from it, ending in it, and breathing in it; and because, as everything constitutes one Self only, there is no room for passion; therefore a man is to meditate with a calm mind. And since the sentence aims at enjoining calmness of mind, it cannot at the same time enjoin meditation on Brahman 1; but meditation is separately enjoined in the clause, 'Let him form the determination, i.e. reflection.' And thereupon the subsequent passage, 'He who consists of mind, whose body is breath,' &c. states the object of the meditation in words indicatory of the individual soul. For this reason we maintain that the meditation spoken of has the individual soul for its object. The other attributes also subsequently stated in the text, 'He to whom all works, all desires belong,' &c. may rightly be held to refer to the individual soul. The attributes, finally, of being what abides in the heart and of being extremely minute which are mentioned in the passage, 'He is my Self within the heart, smaller than a corn of rice, smaller than a corn of barley,' may be ascribed to the individual soul which has the size of the point of a goad, but not to the unlimited Brahman. If it be objected that the immediately following passage, 'greater than the earth,' &c., cannot refer to something limited, we reply that smallness and greatness which are mutually opposite cannot indeed be ascribed to one and the same thing; and that, if one attribute
only is to be ascribed to the subject of the passage, smallness is preferable because it is mentioned first; while the greatness mentioned later on may be attributed to the soul in so far as it is one with Brahman. If it is once settled that the whole passage refers to the individual soul, it follows that the declaration of Brahman also, contained in the passage, 'That is Brahman' (III, 14, 4), refers to the individual soul 1, as it is clearly connected with the general topic. Therefore the individual soul is the object of meditation indicated by the qualities of consisting of mind and so on.
To all this we reply: The highest Brahman only is what is to be meditated upon as distinguished by the attributes of consisting of mind and so on.--Why?--'On account of there being taught here what is known from everywhere.' What is known from all Vedânta-passages to be the sense of the word Brahman, viz. the cause of the world, and what is mentioned here in the beginning words of the passage, ('all this indeed is Brahman,') the same we must assume to be taught here as distinguished by certain qualities, viz. consisting of mind and so on. Thus we avoid the fault of dropping the subject-matter under discussion and needlessly introducing a new topic.--But, it may be said, it has been shown that Brahman is, in the beginning of the passage, introduced merely for the purpose of intimating the injunction of calmness of mind, not for the purpose of intimating Brahman itself.--True, we reply; but the fact nevertheless remains that, where the qualities of consisting of mind, &c. are spoken of, Brahman only is proximate (i.e. mentioned not far off so that it may be concluded to be the thing referred to), while the individual soul is neither proximate nor intimated by any word directly pointing to it. The cases of Brahman and the individual soul are therefore not equal.
108:1 The clause 'he is to meditate with a calm mind' if taken as a gunavidhi, i.e. as enjoining some secondary matter, viz. calmness of mind of the meditating person, cannot at the same time enjoin meditation; for that would involve a so-called split of the sentence (vâkyabheda).
109:1 Gîve#pi dehâdibrimhanâg gyâstvanyâyâd vâ brahmatety arthah. Ân. Gi.