The Vedanta Sutras of Badarayana, Commentary by Sankara (SBE38), tr. by George Thibaut [1896] at sacred-texts.com
12. Should you say that on account of the denial (made by scripture) (the soul of him who knows Brahman does not depart); we deny this, (because scripture means to say that the prânas do not depart) from the embodied soul.
From the distinction conveyed by the clause, 'and (relative) immortality without having burned' (Sûtra 7), it follows that in the case of absolute immortality being reached there is no going and no departure of the soul from the body.--The idea that for some reason or other
a departure of the soul might take place in this latter case also, is precluded by the following scriptural passage, 'But as to the man who does not desire, who, not desiring, freed from desires, is satisfied in his desires, or desires the Self only, of him the vital spirits do not depart,--being Brahman, he goes to Brahman' (Bri. Up. IV, 4, 6). From this express denial--forming part of the higher knowledge--it follows that the prânas do not pass out of the body of him who knows Brahman.
This conclusion the pûrvapakshin denies. For, he says, the passage quoted does not deny the departure of the prânas from the body, but from the embodied (individual) soul.--How is this known?--From the fact that in another Sâkhâ we have (not the sixth, genitive, case 'of him,' but) the fifth, ablative, case 'from him'--'From him the vital spirits do not depart' (Mâdhyandina Sâkhâ). For the sixth case which expresses only relation in general is determined towards some special relation by the fifth case met with in another Sâkhâ. And as the embodied soul which has a claim on exaltation and bliss is the chief topic of the chapter, we construe the words 'from him' to mean not the body but the embodied soul. The sense therefore is 'from that soul when about to depart the prânas do not depart, but remain with it.' The soul of him who dies therefore passes out of the body, together with the prânas. This view the next Sûtra refutes.