CC Ādi 2.56

sei tina janera tumi parama āśraya
tumi mūla nārāyaṇa — ithe ki saṁśaya
Word for word: 
sei — these; tina — three; janera — of the plenary portions; tumi — You; parama — ultimate; āśraya — shelter; tumi — You; mūla — primeval; nārāyaṇa — Nārāyaṇa; ithe — in this; ki — what; saṁśaya — doubt.
Translation: 
“You are the ultimate shelter of these three plenary portions. Thus there is not the slightest doubt that You are the primeval Nārāyaṇa.
Purport: 

Brahmā has confirmed that Lord Kṛṣṇa is the Supreme, the source of the three manifestations known as Kṣīrodakaśāyī Viṣṇu, Garbhodakaśāyī Viṣṇu and Kāraṇodakaśāyī Viṣṇu (Mahā-Viṣṇu). For His pastimes, Lord Kṛṣṇa has four original manifestations — namely Vāsudeva, Saṅkarṣaṇa, Pradyumna and Aniruddha. The first puruṣa-avatāra, Mahā-Viṣṇu in the Causal Ocean, who is the creator of the aggregate material energy, is an expansion of Saṅkarṣaṇa; the second puruṣa, Garbhodakaśāyī Viṣṇu, is an expansion of Pradyumna; and the third puruṣa, Kṣīrodakaśāyī Viṣṇu, is an expansion of Aniruddha. All these are within the category of manifestations of Nārāyaṇa, who is a manifestation of Śrī Kṛṣṇa.