The Vedanta Sutras of Badarayana, Commentary by Sankara (SBE38), tr. by George Thibaut  at sacred-texts.com
16. (What scripture says about absence of all specific cognition) refers either to deep sleep or union (release); for this is manifested (by the texts).
By 'entering into one's own Self' is meant dreamless
sleep; according to the text, 'He is gone to his own Self, he sleeps they say' (Kh. Up. VI, 8, 1). 'Union' means blissful isolation (final release), according to the text, 'Being Brahman he goes to Brahman' (Bri. Up. IV, 4, 6). What the texts say about absence of specific cognition is said with reference to either of those two states, dreamless sleep or final release.--How do we know this?--Because this is 'manifest,' owing to the fact that those two states form the topic there (where absence of all cognition is mentioned). Compare the passages, 'Having risen from out of these elements it perishes again after them. Having departed there is no more knowledge;' 'But where the Self only is all this;' 'Where when asleep he desires no more desires, and dreams no more dreams' (Bri. Up. II, 4, 12; IV, 5, 15; IV, 3, 19).--Those passages, on the other hand, which describe lordly power refer to an altogether different condition, which--like the heavenly world and so on--is an abode where qualified knowledge produces its results.--Thus there is no contradiction.