The Vedanta Sutras, commentary by Sankaracharya (SBE34), tr. by George Thibaut [1890] at sacred-texts.com
28. Gaimini (declares that there is) no contradiction even on the assumption of a direct (worship of the highest Lord as Vaisvânara).
Above (Sûtra 26) it has been said that Vaisvânara is the highest Lord, to be meditated upon as having the gastric fire either for his outward manifestation or for his limiting condition; which interpretation was accepted in deference to the circumstance that he is spoken of as abiding within--and so on.--The teacher Gaimini however is of opinion that it is not necessary to have recourse to the assumption of an outward manifestation or limiting condition, and that there is no objection to refer the passage about Vaisvânara to the direct worship of the highest Lord.--But, if you reject the interpretation based on the gastric fire, you place yourself in opposition to the statement that Vaisvânara abides within, and to the reasons founded on the term, &c. (Sû. 26).--To this we reply that we in no way place ourselves in opposition to the statement that Vaisvânara abides within. For the passage, 'He knows him as man-like, as abiding within man,' does not by any means refer to the gastric fire, the latter being neither the general topic of discussion nor having been mentioned by name before.--What then does it refer to?--It refers to that which forms the subject of discussion, viz. that similarity to man (of the highest Self) which is fancifully found in the members of man from the upper part of the head down to the chin; the text therefore says, 'He knows him as man-like,
as abiding within man,' just as we say of a branch that it abides within the tree 1.--Or else we may adopt another interpretation and say that after the highest Self has been represented as having the likeness to man as a limiting condition, with regard to nature as well as to man, the passage last quoted ('He knows him as abiding within man') speaks of the same highest Self as the mere witness (sâkshin; i.e. as the pure Self, non-related to the limiting conditions).--The consideration of the context having thus shown that the highest Self has to be resorted to for the interpretation of the passage, the term 'Vaisvânara' must denote the highest Self in some way or other. The word 'Visvânara' is to be explained either as 'he who is all and man (i.e. the individual soul),' or 'he to whom souls belong' (in so far as he is their maker or ruler), and thus denotes the highest Self which is the Self of all. And the form 'Vaisvânara' has the same meaning as 'Visvânara,' the taddhita-suffix, by which the former word is derived from the latter, not changing the meaning; just as in the case of râkshasa (derived from rakshas), and vâyasa (derived from vayas).--The word 'Agni' also may denote the highest Self if we adopt the etymology agni = agranî, i.e. he who leads in front.--As the Gârhapatya-fire finally, and as the abode of the oblation to breath the highest Self may be represented because it is the Self of all.
But, if it is assumed that Vaisvânara denotes the highest Self, how can Scripture declare that he is measured by a span?--On the explanation of this difficulty we now enter.
150:1 Whereby we mean not that it is inside the tree, but that it forms a part of the tree.--The Vaisvânara Self is identified with the different members of the body, and these members abide within, i.e. form parts of the body.