The Vedanta Sutras of Badarayana, Commentary by Sankara (SBE38), tr. by George Thibaut  at sacred-texts.com
17. The (living) Self is not (produced) as there is no scriptural statement, and as it is eternal according to them (i.e. scriptural passages).
There is a Self called the living one (the individual soul), which rules the body and the senses, and is connected with the fruits of actions. With regard to that Self the conflict of scriptural passages suggests the doubt, whether it is produced from Brahman like ether and the other elements, or if, like Brahman itself, it is unproduced. Some scriptural passages, by comparing it to sparks proceeding from a fire and so on, intimate that the living soul is produced
from Brahman; from others again we learn that the highest Brahman, without undergoing any modification, passes, by entering into its effects (the elements), into the condition of the individual soul. These latter passages do not thus record an origination of the individual soul.
The pûrvapakshin maintains that the individual soul is produced, because on that view the general promissory statement is not contradicted. For the general assertion that 'by one thing being known all this is known' is not contradicted, only if the entire aggregate of things springs from Brahman; while it would be contradicted by the assumption of the individual soul being a thing of a different kind. Nor can the individual soul be conceived as mere unmodified highest Self, on account of the difference of their respective characteristics. For the highest Self is characterised by freedom from sin and so on, while the individual soul possesses the opposite attributes. That it is an effect, follows moreover from its being divided. For ether and all other things, in so far as divided, are effects, and we have concluded therefrom that they have an origin. Hence the soul also, which is distributed through all the bodies, doing good and evil and experiencing pleasure and pain, must be considered to originate at the time when the entire world is produced. We have moreover the following scriptural passage, 'As small sparks come forth from fire, thus from that Self all vital airs,' &c. (Bri. Up. II, 1, 20). This text teaches first the creation of the aggregate of objects of fruition, beginning with the vital airs, and then (in the words, 'all the Selfs') separately teaches the creation of all the enjoying souls. Again we have the passage, 'As from a blazing fire sparks, being of the same nature as fire, fly forth a thousandfold, thus are various beings brought forth from the Imperishable, my friend, and return hither also' (Mu. Up. II, 1, 1); a passage descriptive of the origin and the retractation of the souls, as we infer from the statement about the sameness of nature 1.
[paragraph continues] For the individual souls are of the same nature as Brahman, because they are endowed with intelligence. Nor can the fact that in some places (as, for instance, in the accounts of the creation of the elements) the creation of the soul is not mentioned, invalidate what is stated about it in other places; it being a general principle of interpretation that whatever new, and at the same time non-contradictory, matter is taught in some scriptural passage has to be combined with the teaching of all other passages. Hence that passage also which speaks of the Self entering (into its effects and thus becoming gîva) must be explained as stating the Self's passing over into an effect (viz. the soul), analogously to such passages as 'that made itself its Self,' &c. (Taitt. Up. II, 7).--From all which it follows that the individual soul is a product.
To all this we reply, that the individual soul is not a product.--Why?--On account of the absence of scriptural statement. For in the chapters which treat of the creation, the production of the soul is, in most cases, not mentioned.--But, it was admitted above that the circumstance of something not being stated in some places does not invalidate the statements made about it elsewhere.--True, that was admitted; but we now declare that the production of the soul is not possible.--Why?--'On account of the eternity, &c., resulting from them' (i.e. the scriptural passages). The word '&c.' implies non-originatedness and similar attributes. For we know from scriptural passages that the soul is eternal, that it has no origin, that it is unchanging, that what constitutes the soul is the unmodified Brahman, and that the soul has its Self in Brahman. A being of such a nature cannot be a product. The scriptural passages to which we are alluding are the following:--'The living Self dies not' (Kh. Up. VI, 11, 3); 'This great unborn Self undecaying, undying, immortal, fearless is indeed Brahman' (Bri. Up. IV, 4, 25); 'The knowing Self is not born, it dies not' (Ka. Up. I, 2, 18); 'The Ancient is unborn, eternal, everlasting' (Ka. Up. I, 2, 18); 'Having sent forth that he entered into it' (Taitt. Up. II, 6); 'Let me now enter those with this living Self and let me then
evolve names and forms' (Kh. Up. VI, 3, 2); 'He entered thither to the very tips of the finger-nails' (Bri. Up. I, 4, 7); 'Thou art that' (Kh. Up. VI, 8, 7); 'I am Brahman' (Bri. Up. II, 4,10); 'This Self is Brahman knowing all' (Bri. Up. II, 5, 19).--All these texts declare the eternity of the soul, and thus militate against the view of its having been produced.--But it has been argued above that the soul must be a modification because it is divided, and must have an origin because it is a modification!--It is not, we reply, in itself divided; for scripture declares that 'there is one God hidden in all beings, all-pervading, the Self within all beings' (Sve. Up. VI, 11); it only appears divided owing to its limiting adjuncts, such as the mind and so on, just as the ether appears divided by its connexion with jars and the like. Scripture (viz. Bri. Up. IV, 4, 5, 'that Self is indeed Brahman, made up of knowledge, mind, life, sight, hearing,' &c.) also declares that the one unmodified Brahman is made up of a plurality of intellects (buddhi), &c. By Brahman being made up of mind and so on is meant, that its nature is coloured thereby, while the fact of its being entirely separate from it is non-apparent. Analogously we say that a mean, cowardly fellow is made up of womanishness.--The casual passages which speak of the soul's production and dissolution must therefore be interpreted on the ground of the soul's connexion with its limiting adjuncts; when the adjunct is produced or dissolved, the soul also is said to be produced or dissolved. Thus scripture also declares, 'Being altogether a mass of knowledge, having risen from out of these elements it again perishes after them. When he has departed there is no more knowledge' (Bri. Up. IV, 5, 13). What is meant there, is only the dissolution of the limiting adjuncts of the Self, not the dissolution of the Self itself 1. The text itself explains this, in reply to Maitreyî's question
[paragraph continues] ('Here, Sir, thou hast landed me in utter bewilderment. Indeed I do not understand him, that when he has departed there is no more knowledge'), in the words, 'I say nothing that is bewildering. Verily, beloved, that Self is imperishable and of an indestructible nature. But it enters into contact with the sense organs.'--Non-contradiction moreover of the general assertion (about everything being known through one) results only from the acknowledgment that Brahman is the individual soul. The difference of the attributes of both is also owing to the limiting adjuncts only. Moreover the words 'Speak on for the sake of final deliverance' (uttered by Ganaka with reference to the instruction he receives from Yâgñavalkya about the vigñâna-maya âtman) implicitly deny that the Self consisting of knowledge (i.e. the individual soul) possesses any of the attributes of transitory existence, and thus show it to be one with the highest Self.--From all this it follows that the individual soul does not either originate or undergo destruction.
30:1 That the word bhâvâh 'beings' here means 'individual souls,' we conclude from their being said to have the same nature as the Imperishable.
32:1 Hence the phrase, 'there is no more knowledge,'--which seems to contradict the term 'a mass of knowledge,'--only means that, on the limiting adjuncts being dissolved, there is no longer any knowledge of distinctions.