The following is taken from the much longer post here which explores this topic in more depth.

Tom: Yes, or rather Shankara in his commentaries speaks of these – Nirguna Brahman (Brahman without objects or without arising phenomena) is the true formless Brahman that exists without any arising phenomena or forms, and when there is ignorance present, we take ourselves to be a body-mind entity living in a world, and that projection of name and form (due to ignorance) is called Saguna Brahman (Brahman with objects or with arising phenomena appearing within it). It is Nirguna Brahman that is to be known, for this is what liberates, not saguna Brahman, which is Brahman plus Maya or Brahman plus ignorance. The latter, saguna Brahman, not only does it not liberate – it doesn’t even truly exist – this is the meaning of ajata vada.

This is explained many times in many places by Shankara in his commentaries, eg. in his commentaries on Brahma Sutras 3.2.14 and 3.2.15 he writes the following, which explains that the true Brahman is nirguna, without name and form, but Brahman is spoken of as saguna (with name and form) for the purposes of meditation and purification of the mind of lower level seekers:

3.2.14: For (Brahman) is merely devoid of form, on account of this being the main purport of scripture.

Shankara's commentary: Brahman, we must definitively assert, is devoid of all form, colour, and so on, and does not in any way possess form, and so on -- why? - 'On account of this being the main purport (of scripture).', 'It is neither coarse nor fine, neither short nor long' (Bṛ. Up. III, 8, 8); 'That which is without sound, without touch, without form, without decay' (Ka. Up. I, 3, 15); 'He who is called ether is the revealer of all forms and names. That within which forms and names are, that is Brahman' (Ch. Up. VIII, 14, 1); 'That heavenly person is without body, he is both without and within, not produced' (Mu. Up. II, 1, 2); 'That Brahman is without cause and without effect, without anything inside or outside, this Self is Brahman, omnipresent and omniscient' (Bṛ. Up. II, 5, 19). These and similar passages have for their purport the true nature of Brahman as non-connected with any world, and have not any other purport, as we have proved under I, 1, 4. On the ground of such passages we therefore must definitively conclude that Brahman is devoid of form. Those other passages, on the other hand, which refer to a Brahman qualified by form do not aim at setting forth the nature of Brahman, but rather at enjoining the worship of Brahman. As long as those latter texts do not contradict those of the former class, they are to be accepted as they stand; where, however, contradictions occur, the passages whose main subject is Brahman must be viewed as having greater force than those of the other kind. This is the reason for our deciding that although there are two different classes of scriptural texts, Brahman must be held to be altogether without form, not at the same time of an opposite nature. But what then is the position of those passages which refer to Brahman as possessing form? To this question the next Sūtra replies.


3.2.15: And as light (assumes forms as it were by its contact with things possessing form, so does Brahman;) since (the texts ascribing form to Brahman) are not devoid of meaning.

Shankara's commentary: Just as the light of the sun or the moon after having passed through space enters into contact with a finger or some other limiting adjunct, and, according as the latter is straight or bent, itself becomes straight or bent as it were; so Brahman also assumes, as it were, the form of the earth and the other limiting adjuncts with which it enters into connexion. Hence there is no reason why certain texts should not teach, with a view to meditative worship, that Brahman has that and that form. We thus escape the conclusion that those Vedic passages which ascribe form to Brahman are devoid of sense; a conclusion altogether unacceptable since all parts of the Veda are equally authoritative, and hence must all be assumed to have a meaning. But does this not imply a contradiction of the tenet maintained above, viz. that Brahman does not possess double characteristics although it is connected with limiting adjuncts? By no means, we reply. What is merely due to a limiting adjunct cannot constitute an attribute of a substance, and the limiting adjuncts are, moreover, projected by Nescience only. That the primeval natural Nescience leaves room for all practical life and activity, whether ordinary or based on the Veda, we have explained more than once.

Tom: Shankara concludes, as he does throughout his many commentaries, that Brahman is to be truly known without form, but Brahman is said to be with form only for purposes of worship (ie. purification of the mind as opposed to self-realisation). He states that the teachings that state Brahman has form do have value in that regard only, but he concludes by reaffirming that name and form and 'practical life' (vyavaharika) only appear/arise due to nescience (ignorance) - ie. that in liberation or Brahma-Vidya, no names and forms arise, ie. nirguna Brahman is to be realised as ones self.