SB 10.3.15-17

yatheme ’vikṛtā bhāvās
 tathā te vikṛtaiḥ saha
nānā-vīryāḥ pṛthag-bhūtā
 virājaṁ janayanti hi
sannipatya samutpādya
 dṛśyante ’nugatā iva
prāg eva vidyamānatvān
 na teṣām iha sambhavaḥ
evaṁ bhavān buddhy-anumeya-lakṣaṇair
 grāhyair guṇaiḥ sann api tad-guṇāgrahaḥ
anāvṛtatvād bahir antaraṁ na te
 sarvasya sarvātmana ātma-vastunaḥ
Word for word: 
yathā — as; ime — these material creations, made of material energy; avikṛtāḥ — actually not disintegrated; bhāvāḥ — with such a conception; tathā — similarly; te — they; vikṛtaiḥ saha — association with these different elements coming from the total material energy; nānā-vīryāḥ — every element is full of different energies; pṛthak — separated; bhūtāḥ — becoming; virājam — the whole cosmic manifestation; janayanti — create; hi — indeed; sannipatya — because of association with the spiritual energy; samutpādya — after being created; dṛśyante — they appear; anugatāḥ — entered within it; iva — as if; prāk — from the very beginning, before the creation of this cosmic manifestation; eva — indeed; vidyamānatvāt — due to the existence of the Supreme Personality of Godhead; na — not; teṣām — of these material elements; iha — in this matter of creation; sambhavaḥ — entering would have been possible; evam — in this way; bhavān — O my Lord; buddhi-anumeya-lakṣaṇaiḥ — by real intelligence and by such symptoms; grāhyaiḥ — with the objects of the senses; guṇaiḥ — with the modes of material nature; san api — although in touch; tat-guṇa-agrahaḥ — are not touched by the material qualities; anāvṛtatvāt — because of being situated everywhere; bahiḥ antaram — within the external and internal; na te — there is no such thing for You; sarvasya — of everything; sarva-ātmanaḥ — You are the root of everything; ātma-vastunaḥ — everything belongs to You, but You are outside and inside of everything.
Translation: 
The mahat-tattva, the total material energy, is undivided, but because of the material modes of nature, it appears to separate into earth, water, fire, air and ether. Because of the living energy [jīva-bhūta], these separated energies combine to make the cosmic manifestation visible, but in fact, before the creation of the cosmos, the total energy is already present. Therefore, the total material energy never actually enters the creation. Similarly, although You are perceived by our senses because of Your presence, You cannot be perceived by the senses, nor experienced by the mind or words [avāṅ-mānasa-gocara]. With our senses we can perceive some things, but not everything; for example, we can use our eyes to see, but not to taste. Consequently, You are beyond perception by the senses. Although in touch with the modes of material nature, You are unaffected by them. You are the prime factor in everything, the all-pervading, undivided Supersoul. For You, therefore, there is no external or internal. You never entered the womb of Devakī; rather, You existed there already.
Purport: 

This same understanding is explained by the Lord Himself in Bhagavad-gītā (9.4):

mayā tatam idaṁ sarvaṁ
 jagad-avyakta-mūrtinā
mat-sthāni sarva-bhūtāni
 na cāhaṁ teṣv avasthitaḥ

“By Me, in My unmanifested form, this entire universe is pervaded. All beings are in Me, but I am not in them.”

The Supreme Personality of Godhead is not perceivable through the gross material senses. It is said that Lord Śrī Kṛṣṇa’s name, fame, pastimes, etc., cannot be understood by material senses. Only to one who is engaged in pure devotional service under proper guidance is He revealed. As stated in Brahma-saṁhitā (5.38):

premāñjana-cchurita-bhakti-vilocanena
 santaḥ sadaiva hṛdayeṣu vilokayanti

One can see the Supreme Personality of Godhead, Govinda, always, within oneself and outside oneself, if one has developed the transcendental loving attitude toward Him. Thus for people in general, He is not visible. In the above-mentioned verse from Bhagavad-gītā, therefore, it is said that although He is all-pervading, everywhere present, He is not conceivable by the material senses. But actually, although we cannot see Him, everything is resting in Him. As discussed in the Seventh Chapter of Bhagavad-gītā, the entire material cosmic manifestation is only a combination of His two different energies, the superior, spiritual energy and the inferior, material energy. Just as the sunshine is spread all over the universe, the energy of the Lord is spread all over the creation, and everything is resting in that energy.

Yet one should not conclude that because He is spread all over He has lost His personal existence. To refute such arguments, the Lord says, “I am everywhere, and everything is in Me, but still I am aloof.” For example, a king heads a government which is but the manifestation of the king’s energy; the different governmental departments are nothing but the energies of the king, and each department is resting on the king’s power. But still one cannot expect the king to be present in every department personally. That is a crude example. Similarly, all the manifestations that we see, and everything that exists, both in this material world and in the spiritual world, are resting on the energy of the Supreme Personality of Godhead. The creation takes place by the diffusion of His different energies, and, as stated in the Bhagavad-gītā, He is everywhere present by His personal representation, the diffusion of His different energies.

One may argue that the Supreme Personality of Godhead, who creates the whole cosmic manifestation simply by His glance, cannot come within the womb of Devakī, the wife of Vasudeva. To eradicate this argument, Vasudeva said, “My dear Lord, it is not very wonderful that You appeared within the womb of Devakī, for the creation was also made in that way. You were lying in the Causal Ocean as Mahā-Viṣṇu, and by Your breathing, innumerable universes came into existence. Then You entered into each of the universes as Garbhodakaśāyī Viṣṇu. Then again You expanded Yourself as Kṣīrodakaśāyī Viṣṇu and entered into the heart of all living entities and entered even within the atoms. Therefore Your entrance into the womb of Devakī is understandable in the same way. You appear to have entered, but You are simultaneously all-pervading. We can understand Your entrance and nonentrance from material examples. The total material energy remains intact even after being divided into sixteen elements. The material body is nothing but a combination of the five gross elements — namely earth, water, fire, air and ether. Whenever there is a material body, it appears that such elements are newly created, but actually the elements are always existing outside of the body. Similarly, although You appear as a child in the womb of Devakī, You are also existing outside. You are always in Your abode, but still You can simultaneously expand Yourself into millions of forms.

“One has to understand Your appearance with great intelligence because the material energy is also emanating from You. You are the original source of the material energy, just as the sun is the source of the sunshine. The sunshine cannot cover the sun globe, nor can the material energy — being an emanation from You — cover You. You appear to be in the three modes of material energy, but actually the three modes of material energy cannot cover You. This is understood by the highly intellectual philosophers. In other words, although You appear to be within the material energy, You are never covered by it.”

We hear from the Vedic version that the Supreme Brahman exhibits His effulgence and therefore everything is illuminated. We can understand from Brahma-saṁhitā that the brahmajyoti, or the Brahman effulgence, emanates from the body of the Supreme Lord. And from the Brahman effulgence, all creation takes place. It is further stated in the Bhagavad-gītā that the Lord is the support of the Brahman effulgence. Originally He is the root cause of everything. But persons who are less intelligent think that when the Supreme Personality of Godhead comes within this material world, He accepts material qualities. Such conclusions are not mature, but are made by the less intelligent.