The Vedanta Sutras of Badarayana, Commentary by Sankara (SBE38), tr. by George Thibaut  at sacred-texts.com
4. (They are) conductors, this being indicated.
With regard to those beginning with light a doubt arises whether they are marks of the road, or places of enjoyment, or leaders of the travelling souls.--The first possible view of the question is that light and so on are marks of the road, because the instruction has that character. For as in ordinary life a man wishing to go to a village or a town is told, 'Go from here to that hill, from there to a fig-tree, from that to a river, from that to a village; after that you will reach the town;' so here the text also says, 'from light to day, from day to the waxing half of the month,' &c.--Or else light and so on may be viewed as places of enjoyment. For the text connects Agni and so on with the word 'world'; 'He comes to the world of Agni,' &c. Now the term 'world' is used to denote places of enjoyment of living beings, as when we say, 'The world of men; the world of the Fathers; the world of the gods.' A Brâhmana passage also says, 'They remain attached to the worlds which consist of day and night' (Sat. Brâ. X, 2, 6, 8). Therefore light and the rest are not conductors. Moreover, they cannot be conductors because they are without intelligence. For in ordinary life intelligent men only are appointed by the king to conduct travellers over difficult roads.
To all this we reply as follows. They must be conductors, because the text indicates this. For we read, 'From the moon to the lightning; there a person that is not a man leads them to Brahman;' which shows their conductorship to be something settled. Should it be objected that this last sentence exhausts itself in conveying its own purport 1; we say No; for the attribute ('that is not a man') has only the meaning of excluding his previously established humanity. Only if in the case of the light and the rest personal conductors are settled, and those of human nature, it is appropriate to use the attribute
[paragraph continues] 'amânava,' to the end of excluding this (previously established) humanity 1.
But mere indication has no force, as there is nothing to prove (that there must be such personal conductors).--To this objection the next Sûtra replies.
387:1 And has not the additional power of indicating, i.e. enabling us to infer that also the beings previously mentioned are 'leaders' of the soul.
388:1 Why should it be specially stated that this 'conducting person' is amânava? Only, because it is a settled matter that the previously mentioned beings are also 'conducting persons,' and at the same time 'mânava.' The last clause therefore does not only directly teach that a person conducts the souls to Brahman, but at the same time 'indicates' that the beings mentioned before in connexion with the road are also 'personal conductors.'