Srimad Bhagavatam Canto 02, Chapter 06, Text 39

SB 2.6.39

sa esa adyah purusah
kalpe kalpe srjaty ajah
atmatmany atmanatmanam
sa samyacchati pati ca
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
That supreme original Personality of Godhead, Lord Sri Krsna, expanding His plenary portion as Maha-Visnu, the first incarnation, creates this manifested cosmos, but He is unborn. The creation, however, takes place in Him, and the material substance and manifestations are all Himself. He maintains them for some time and absorbs them into Himself again.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
The creation is nondifferent from the Lord, and still He is not in the creation. This is explained in the Bhagavad-gita (9.4) as follows:
maya tatam idam sarvam
 jagad avyakta-murtina
mat-sthani sarva-bhutani
 na caham tesv avasthitah
The impersonal conception of the Absolute Truth is also a form of the Lord called avyakta-murti. Murti means “form,” but because His impersonal feature is inexplicable to our limited senses, He is the avyakta-murti form, and in that inexplicable form of the Lord the whole creation is resting; or, in other words, the whole creation is the Lord Himself, and the creation is also nondifferent from Him, but simultaneously He, as the original Personality of Godhead Sri Krsna, is aloof from the created manifestation. The impersonalist gives stress to the impersonal form or feature of the Lord and does not believe in the original personality of the Lord, but the Vaisnavas accept the original form of the Lord, of whom the impersonal form is merely one of the features. The impersonal and personal conceptions of the Lord are existing simultaneously, and this fact is clearly described both in the Bhagavad-gita and in the Srimad-Bhagavatam, and also in other Vedic scriptures. Inconceivable to human intelligence, the idea must simply be accepted on the authority of the scriptures, and it can only be practically realized by the progress of devotional service unto the Lord, and never by mental speculation or inductive logic. The impersonalists depend more or less on inductive logic, and therefore they always remain in darkness about the original Personality of Godhead Sri Krsna. Their conception of Krsna is not clear, although everything is clearly mentioned in all the Vedic scriptures. A poor fund of knowledge cannot comprehend the existence of an original personal form of the Lord when He is expanded in everything. This imperfectness is due, more or less, to the material conception that a substance distributed widely in parts can no longer exist in the original form.
The original Personality of Godhead (adyah), Govinda, expands Himself as the Maha-Visnu incarnation and rests in the Causal Ocean, which He Himself creates. The Brahma-samhita (5.47) confirms this as follows:
yah karanarnava-jale bhajati sma yoga-
 nidram ananta-jagad-anda-saroma-kupah
adhara-saktim avalambya param sva-murtim
 govindam adi-purusam tam aham bhajami
Lord Brahmaji says in his Brahma-samhita, “I worship the primeval Lord Govinda, who lies down in the Causal Ocean in His plenary portion as Maha-Visnu, with all the universes generating from the pores of hair on His transcendental body, and who accepts the mystic slumber of eternity.”
So this Maha-Visnu is the first incarnation in the creation, and from Him all the universes are generated and all material manifestations are produced, one after another. The Causal Ocean is created by the Lord as the mahat-tattva, as a cloud in the spiritual sky, and is only a part of His different manifestations. The spiritual sky is an expansion of His personal rays, and He is the mahat-tattva cloud also. He lies down and generates the universes by His breathing, and again, by entering into each universe as Garbhodakasayi Visnu, He creates Brahma, Siva and many other demigods for maintenance of the universe and again absorbs the whole thing into His person as confirmed in the Bhagavad-gita (9.7):
sarva-bhutani kaunteya
 prakrtim yanti mamikam
kalpa-ksaye punas tani
 kalpadau visrjamy aham
“O son of Kunti, when the kalpa, or the duration of the life of Brahma, is ended, then all the created manifestations enter into My prakrti, or energy, and again, when I desire, the same creation takes place by My personal energy.”
The conclusion is that these are all but displays of the Lord’s inconceivable personal energies, of which no one can have any full information. This point we have already discussed.
Srimad Bhagavatam Canto 02, Chapter 06, Text 38
Srimad Bhagavatam Canto 02, Chapter 06, Text 40-41