The Vedanta Sutras of Badarayana, Commentary by Sankara (SBE38), tr. by George Thibaut [1896] at sacred-texts.com
21. If it be said that (texts such as the one about the udgîtha are) mere glorification, on account of their reference (to parts of sacrifices); we deny that, on account of the newness (of what they teach, if viewed as injunctions).
'That udgîtha is the best of all essences, the highest, holding the highest place, the eighth' (Kh. Up. I, 1, 3); 'This earth is the Rik, the fire is Sâman' (Kh. Up. I, 6, 1); 'This world in truth is that piled-up fire-altar' (Sat. Brâ. X, I, 2, 2); 'That hymn is truly that earth' (Ait. Âr. II, 1, 2, 1); with reference to these and other similar passages a doubt arises whether they are meant to glorify the udgîtha and so on, or to enjoin devout meditations.
The pûrvapakshin maintains that their aim is glorification, because the text exhibits them with reference to subordinate members of sacrificial actions, such as the udgîtha and so on. They are, he says, analogous to passages such as 'This earth is the ladle;' 'the sun is the tortoise;' 'the heavenly world is the Âhavanîya,' whose
aim it is to glorify the ladle and so on. To this the Sûtrakâra replies as follows. We have no right to consider the purpose of those passages to be mere glorification, on account of the newness. If they aim at injunction, a new matter is enjoined by them; if, on the other hand, they aimed at glorification they would be devoid of meaning. For, as explained in the Pû. Mîm. Sû., glorificatory passages are of use in so far as entering into a complementary relation to injunctive passages; but the passages under discussion are incapable of entering into such a relation to the udgîtha and so on which are enjoined in altogether different places of the Veda, and would therefore be purposeless as far as glorification is concerned. Passages such as 'This earth is the ladle' are not analogous because they stand in proximity to injunctive passages.--Therefore texts such as those under discussion have an injunctive purpose.