The Vedanta Sutras of Badarayana, Commentary by Sankara (SBE38), tr. by George Thibaut  at sacred-texts.com
33. (The statement as to Brahman having size) subserves the purpose of the mind; in the manner of the four feet (quarters).
In reply to the pûrvapakshin's contention that the statements as to Brahman's size, prove that there exists something different from Brahman, we remark that those statements merely serve the purposes of the mind, i.e. of devout meditation.--But how can the cognition of something consisting
of four, or eight, or sixteen parts be referred to Brahman?--Through its modifications (effects), we reply, Brahman is assumed to be subject to measure. For as some men are of inferior, others of middling, others again of superior intelligence, not all are capable of fixing their mind on the infinite Brahman, devoid of all effects. 'In the manner of the four feet,' i.e. in the same way as (Kh. Up. III, 18), for the purpose of pious meditation, speech and three other feet are ascribed to mind viewed as the personal manifestation of Brahman, and fire and three other feet to the ether viewed as the cosmic manifestation of Brahman.--Or else the phrase, 'in the manner of the four quarters,' may be explained as follows. In the same way as to facilitate commerce, a kârshâpana is assumed to be divided into four parts--for there being no fixed rule as to the value of bargains, people cannot always carry on their transactions with whole kârshâpanas only--, (so, in order to facilitate pious meditation on the part of less intelligent people, four feet, &c., are ascribed to Brahman).