SB 2.8.8

āsīd yad-udarāt padmaṁ
 loka-saṁsthāna-lakṣaṇam
yāvān ayaṁ vai puruṣa
 iyattāvayavaiḥ pṛthak
tāvān asāv iti proktaḥ
 saṁsthāvayavavān iva
Synonyms: 
āsīt — as it grew; yat-udarāt — from whose abdomen; padmam — lotus flower; loka — world; saṁsthāna — situation; lakṣaṇam — possessed of; yāvān — as it were; ayam — this; vai — certainly; puruṣaḥ — the Supreme Personality of Godhead; iyattā — measurement; avayavaiḥ — by embodiments; pṛthak — different; tāvān — so; asau — that; iti proktaḥ — it is so said; saṁsthā — situation; avayavavān — embodiment; iva — like.
Translation: 
If the Supreme Personality of Godhead, from whose abdomen the lotus stem sprouted, is possessed of a gigantic body according to His own caliber and measurement, then what is the specific difference between the body of the Lord and those of common living entities?
Purport: 

One should note how Mahārāja Parīkṣit intelligently put questions before his spiritual master for scientific understanding of the transcendental body of the Lord. It has been described in many places before this that the Lord assumed a gigantic body, like that of Kāraṇodakaśāyī Viṣṇu, from whose hair pores innumerable universes have generated. The body of Garbhodakaśāyī Viṣṇu is described as sprouting the lotus stem within which all the planets of the universe remain, and at the top of the stem is the lotus flower on which Lord Brahmā is born. In the creation of the material world the Supreme Lord undoubtedly assumes a gigantic body, and living entities also get bodies, big or small, according to necessity. For example, an elephant gets a gigantic body according to its needs, and so also an ant gets its body according to its needs. Similarly, if the Personality of Godhead assumes a gigantic body to accommodate the universes or the planets of a particular universe, there is no difference in the principle of assuming or accepting a particular type of body in terms of necessity. A living being and the Lord cannot be distinguished simply by the difference in the magnitude of the body. So the answer depends on the specific significance of the body of the Lord, as distinguished from the body of the common living being.