The Vedanta Sutras of Badarayana, Commentary by Sankara (SBE38), tr. by George Thibaut  at sacred-texts.com
3. But as the Self (scriptural texts) acknowledge and make us comprehend (the Lord).
The Sûtrakâra now considers the question whether the highest Self whose characteristics scripture declares is
to be understood as the 'I' or as different from me.--But how can a doubt arise, considering that scripture exhibits the term 'Self' whose sphere is the inward Self?--This term 'Self'--a reply may be given--may be taken in its primary sense, provided it be possible to view the individual soul and the Lord as non-different; but in the other case the term has to be taken in a secondary (metaphorical) sense only 1.
The pûrvapakshin maintains that the term 'Self is not to be taken as meaning the 'I.' For that which possesses the qualities of being free from all evil, &c., cannot be understood as possessing qualities of a contrary nature, nor can that which possesses those contrary qualities be understood as being free from all evil and so on. But the highest Lord possesses the qualities of being free from all evil, &c., and the embodied Self is characterised by qualities of a contrary nature.--Moreover, if the transmigrating soul constituted the Self of the Lord, it would follow that he is no Lord, and thus scripture would lose its meaning; while, if the Lord constituted the Self of the individual soul, the latter would not be entitled (to works and knowledge), and scripture would thus also lose its meaning. The latter assumption would moreover run counter to perception and the other means of proof.--Should it be said that, although the Lord and the soul are different, they yet must be contemplated as identical, on the basis of scripture, just as Vishnu and other divinities are contemplated in images and so on; the answer is that this contemplation may take place, but that therefrom we must not conclude that the Lord is the real Self of the transmigrating soul.
To all this we make the following reply. The highest Lord must be understood as the Self. For in a chapter treating of the highest Lord the Gâbâlas acknowledge him to be the Self, 'Thou indeed I am. O holy divinity; I indeed thou art, O divinity!'--In the same light other
texts have to be viewed, which also acknowledge the Lord as the Self, such as 'I am Brahman' (Bri. Up. I, 4, 10). Moreover certain Vedânta-texts make us comprehend the Lord as the Self, 'Thy Self is this which is within all' (Bri. Up. III. 4, 1); 'He is thy Self, the ruler within, the immortal' (Bri. Up. III, 7, 3); 'That is the True, that is the Self, thou art that' (Kh. Up. VI, 8, 7).--Nor can we admit the truth of the assertion, made by the pûrvapakshin, that all these passages teach merely a contemplation (of the Lord) in certain symbols, analogous to the contemplation of Vishnu in an image. For that would firstly involve that the texts have not to be understood in their primary sense 1; and in the second place there is a difference of syntactical form. For where scripture intends the contemplation of something in a symbol, it conveys its meaning through a single enunciation such as 'Brahman is Mind' (Kh. Up. III, 18, 1), or 'Brahman is Âditya' (Kh. Up. III, 10, 1). But in the passage quoted above, scripture says, 'I am Thou and thou art I.' As here the form of expression differs from that of texts teaching the contemplation of symbols, the passage must be understood as teaching non-difference. This moreover follows from the express prohibition of the view of difference which a number of scriptural texts convey. Compare e.g. 'Now if a man worships another deity, thinking the deity is one and he another, he does not know' (Bri. Up. I, 4, 10); 'From death to death goes he who here perceives any diversity' (Bri. Up. IV, 4, 19); 'Whosoever looks for anything elsewhere than in the Self is abandoned by everything' (Bri. Up. II, 4, 6).--Nor is there any force in the objection that things with contrary qualities cannot be identical; for this opposition of qualities can be shown to be false.--Nor is it true that from our doctrine it would follow that the Lord is not a Lord. For in these matters scripture alone is authoritative, and we, moreover, do not at all admit that scripture teaches the Lord to be the Self of the transmigrating
soul, but maintain that by denying the transmigrating character of the soul it aims at teaching that the soul is the Self of the Lord. From this it follows that the non-dual Lord is free from all evil qualities, and that to ascribe to him contrary qualities is an error.--Nor is it true that the doctrine of identity would imply that nobody is entitled to works, &c., and is contrary to perception and so on. For we admit that before true knowledge springs up, the soul is implicated in the transmigratory state, and that this state constitutes the sphere of the operation of perception and so on. On the other hand texts such as 'But when the Self only has become all this, how should he see another?' &c., teach that as soon as true knowledge springs up, perception, &c., are no longer valid.--Nor do we mind your objecting that if perception, &c., cease to be valid, scripture itself ceases to be so; for this conclusion is just what we assume. For on the ground of the text, 'Then a father is not a father' up to 'Then the Vedas are not Vedas' (Bri. Up. IV, 3, 22), we ourselves assume that when knowledge springs up scripture ceases to be valid.--And should you ask who then is characterised by the absence of true knowledge, we reply: You yourself who ask this question!--And if you retort, 'But I am the Lord as declared by scripture,' we reply, 'Very well, if you have arrived at that knowledge, then there is nobody who does not possess such knowledge.'--This also disposes of the objection, urged by some, that a system of non-duality cannot be established because the Self is affected with duality by Nescience.
Hence we must fix our minds on the Lord as being the Self.
338:1 And in that case the identity of the highest Self and the 'I' would not follow from the term 'Self.'
339:1 And this is objectionable as long as it has not been demonstrated that the primary meaning is altogether inadmissable.