The Vedanta Sutras of Badarayana, Commentary by Sankara (SBE38), tr. by George Thibaut  at sacred-texts.com
7. Or (the souls' being the food of the gods is) metaphorical, on account of their not knowing the Self. For thus (scripture) declares.
The word 'or' is meant to set aside the started objection. The souls' being food has to be understood in a metaphorical, not a literal, sense, as otherwise all scriptural statements of claims (adhikâra)--such as 'He who is desirous of the heavenly world is to sacrifice'--would be contradicted. If
the performers of sacrifices, &c., did not, in the sphere of the moon, enjoy the fruits of their works, why should they undertake works such as sacrifices, which are to him who performs them the cause of great trouble? We see, moreover, that the word 'food,' as denoting in general whatever is the cause of enjoyment, is metaphorically used of that also which is not food (in the narrower sense), as, for instance, in such phrases as 'the Vaisyas are the food of kings, the animals are the food of the Vaisyas.' Hence what is meant there by the term 'eating' is the rejoicing of the gods with the performers of sacrifices, &c., who stand in a subordinate (instrumental) relation to that rejoicing--a rejoicing analogous to that of an ordinary man with beloved persons such as wife, children, friends, and so on--not actual eating like the chewing and swallowing of sweetmeats. For that the gods eat in the ordinary way a scriptural passage expressly denies (Kh. Up. III, 6, 1), 'The gods do not eat or drink; by seeing the nectar they are satisfied.' At the same time the performers of sacrifices, although standing in a subordinate relation to the gods. may themselves be in a state of enjoyment, like servants who (although subordinate to the king) themselves live on the king.--That the performers of sacrifices are objects of enjoyment for the gods follows, moreover, from their quality of not knowing the Self. For that those who do not know the Self are objects of enjoyment for the gods the following scriptural passage shows, 'Now, if a man worships another deity, thinking the deity is one and he is another, he does not know. He is like a beast for the Devas' (Bri. Up. I, 4, 10). That means: he, in this life, propitiating the gods by means of oblations and other works, serves them like a beast, and does so in the other world also, depending on them like a beast and enjoying the fruits of his works as assigned by them.--The latter part of the Sûtra can be explained in another manner also 1. Those who do not know the Self are those who perform works only, such as sacrifices, &c.,
and do not join knowledge to works. We then take the expression, 'the knowledge of the Self,' as indirectly denoting the knowledge of the five fires; an explanation which rests on the general subject-matter. And on account of the performers of sacrifices being destitute of the knowledge of the five fires the circumstance of their serving as food is brought forward as a mere gunavâda 1 for the purpose of glorifying the knowledge of the five fires. For the latter is what the text aims at enjoining, as we infer from the general purport of the passage.--'For thus' another scriptural passage 'declares,' viz. that enjoyment (on the part of the gîva) takes place in the sphere of the moon, 'Having enjoyed greatness in the Soma world he returns again' (Pr. Up. V, 4). Another scriptural passage also declares that the performers of sacrifices dwelling together with the gods obtain enjoyment, 'A hundred blessings of the fathers who have conquered this world make one blessing of the work-gods, who obtain their godhead by work' (Bri. Up. IV, 3. 33).--As thus the statement about the performers of sacrifices becoming food is metaphorical only, we understand that it is their souls which go, and hence there is no longer any objection to the doctrine that they go enveloped by water.
111:1 Anâtmasabdasruter mukhyârthatvânurodhena sûtrâmsasyârtham uktvâ prakaranânurodhenârthântaram âha. Ân. Gi.
112:1 See part i, p. 221.