The Vedanta Sutras of Badarayana, Commentary by Sankara (SBE38), tr. by George Thibaut  at sacred-texts.com
REVERENCE TO THE HIGHEST SELF!
1. On the road beginning with light (the departed soul proceeds), on account of that being widely known.
It has been explained that up to the beginning of the way, the departure is the same. About the way itself, however, different texts make different declarations. One passage describes it as constituted by the junction of the veins and rays, 'Then he mounts upwards by just those rays' (Kh. Up. VIII, 6, 5), Another passage describes it as beginning with light, 'They go to the light, from light to day' (Kh. Up. V, 10, 1). Another way is described, Kau. Up. I, 3, 'Having reached the path of the gods, he comes to the world of Agni.' Another, Bri. Up. V, 10, 1, 'When the person goes away from this world, he comes to the wind.' Another again. Mu. Up. I, 2, 11, 'Free from passions they depart through the gate of the sun.' A doubt here arises whether these ways are different from each other, or whether there is only one road of which the different texts mention different particulars.--The pûrvapakshin embraces the former alternative, for the reason that those roads are referred to in different chapters and form parts of different meditations. If, moreover, we regarded the statements about light and so on, the emphatical assertion 1 made in the first of the passages quoted above would be contradicted; and the statement about the quickness of mounting, 'As quickly as he sends off the mind he goes to the sun,' would also be interfered with. We therefore conclude that the roads described are different roads. To this we reply, 'On the road beginning with light;'
i.e. we maintain that every one who desires to reach Brahman moves on the road beginning with light.--Why so?--'On account of its being widely known.' That road is known to all who possess knowledge. Thus the chapter of the vidyâ of the five fires ('And those also who in the forest meditate on the True as faith,' &c., Bri. Up. VI, 2, 15) expressly states that the road beginning with the light belongs to those also who practise other meditations.--That road, an objection is raised, may present itself to the mind in the case of those meditations which do not mention any road of their own; but why should it be accepted for such meditations as mention different roads of their own?--This objection would be valid, we reply, if the various roads mentioned were entirely different; but as a matter of fact there is only one road leading to the world of Brahman and possessing different attributes; and this road is designated in one place by one attribute and in another place by another attribute. For this relation of attributes and what possesses attributes is established by the circumstance that we recognise, in all the passages quoted, some part of the road 1. And if the chapters which mention the roads are different, we, as long as the meditation is one, have to combine the different attributes of the road (mentioned separately in the different chapters), in the same way as (in general) the different particulars of one meditation (which are stated in different chapters) have to be combined. And even if the meditations (in which the particulars of the road are mentioned) are different, the road must be viewed as one and the same, because we recognise everywhere some part of the road and because the goal is everywhere the same. For all the following passages declare one and the same result, viz. the obtainment of the world of Brahman: 'In these worlds of Brahman they dwell for ever and ever' (Bri. Up. VI, 2, 15); 'There he dwells eternal years' (Bri. Up. V, 10, 1);
[paragraph continues] 'Whatever victory, whatever greatness belongs to Brahman, that victory he gives, that greatness he reaches' (Kau. Up. I, 2); 'Those who find the world of Brahman by Brahmakarya' (Kh. Up. VIII, 4, 3).--To the remark that the emphatical assertion (made in the passage, 'Just by those rays,' &c.) would be contradicted by our admitting light and so on as stages of the road, we reply that no such difficulty exists, because that passage aims only at establishing the rays (as part of the road). For the one word 'just' cannot at the same time establish the rays and discard light and so on. The passage therefore must be understood as only emphasising the connexion with the rays.--Nor does the regard paid by us to the statements about light and so on being stages of the way contradict what one passage says about speed; for that passage means to say that one goes (to the world of Brahman) more quickly than anywhere else, so that its sense is, 'In the twinkling of an eye one goes there 1.'--Moreover the passage, 'On neither of these two ways' (Kh. Up. V, 10, 8)--in teaching that there is a third inferior road for those who have missed the other two roads--shows that besides the road of the fathers there is only one further road, viz. the road of the gods, of which light and so on are stages. The text about light and so on mentioning a greater number of stages while other texts mention a smaller number, it stands to reason that the less numerous should be explained in conformity, with the more numerous. For this reason also the Sûtra says, 'On the road beginning with light, on account of its being widely known.'
382:1 The emphasis lies in the word 'eva,' i.e. 'just' or 'only,' which seems to exclude any stages of the way but those rays.
383:1 Each passage mentions at least one of the stages of the road leading to the world of Brahman, and we thus conclude that the same road--of which the stations are the attributes--is meant everywhere.
384:1 Read in the text--tvarâvakanam tv arkirâdyapekshâyâm api gantavyântarâpekshayâ kshaipryârtha°.--Ânandagiri comments--tvareti, arkirâdimârgasyaikyeऽpi kutaskid anyato gantavyâd anenopâyena satyalokam gat iti gakkhantîti gantavyabhedâpekshayâ vakanam yuktam ity arthah.