The Vedanta Sutras, commentary by Sankaracharya (SBE34), tr. by George Thibaut  at sacred-texts.com
5. And if you maintain that the text does speak (of the pradhâna as an object of knowledge) we deny that; for the intelligent (highest) Self is meant, on account of the general subject-matter.
Here the Sânkhya raises a new objection, and maintains that the averment made in the last Sûtra is not proved, since the text later on speaks of the pradhâna--which had been referred to as the Undeveloped--as an object of knowledge. 'He who has perceived that which is without sound, without touch, without form, without decay, without taste, eternal, without smell, without beginning, without end, beyond the great and unchangeable, is freed from the jaws of death' (Ka. Up. II, 3, 15). For here the text speaks of the pradhâna,
which is beyond the great, describing it as possessing the same qualities which the Sânkhya-smriti ascribes to it, and designating it as the object of perception. Hence we conclude that the pradhâna is denoted by the term avyakta.
To this we reply that the passage last quoted does represent as the object of perception not the pradhâna but the intelligent, i.e. the highest Self. We conclude this from the general subject-matter. For that the highest Self continues to form the subject-matter is clear from the following reasons. In the first place, it is referred to in the passage, 'Beyond the person there is nothing, this is the goal, the highest Road;' it has further to be supplied as the object of knowledge in the passage, 'The Self is hidden in all beings and does not shine forth,' because it is there spoken of as difficult to know; after that the restraint of passion, &c. is enjoined as conducive to its cognition, in the passage, 'A wise man should keep down speech within the mind;' and, finally, release from the jaws of death is declared to be the fruit of its knowledge. The Sânkhyas, on the other hand, do not suppose that a man is freed from the jaws of death merely by perceiving the pradhâna, but connect that result rather with the cognition of the intelligent Self.--The highest Self is, moreover, spoken of in all Vedânta-texts as possessing just those qualities which are mentioned in the passage quoted above, viz. absence of sound, and the like. Hence it follows, that the pradhâna is in the text neither spoken of as the object of knowledge nor denoted by the term avyakta.