CC Madhya 20.251

viṣṇos tu trīṇi rūpāṇi
puruṣākhyāny atho viduḥ
ekaṁ tu mahataḥ sraṣṭṛ
dvitīyaṁ tv aṇḍa-saṁsthitam
tṛtīyaṁ sarva-bhūta-sthaṁ
tāni jñātvā vimucyate
Synonyms: 
viṣṇoḥ — of Lord Viṣṇu; tu — certainly; trīṇi — three; rūpāṇi — forms; puruṣa-ākhyāni — celebrated as the puruṣas; atho — how; viduḥ — they know; ekam — one of them; tu — but; mahataḥ sraṣṭṛ — the creator of the total material energy; dvitīyam — the second; tu — but; aṇḍa-saṁsthitam — situated within the universe; tṛtīyam — the third; sarva-bhūta-stham — within the hearts of all living entities; tāni — these three; jñātvā — knowing; vimucyate — one becomes liberated.
Translation: 
“ ‘Viṣṇu has three forms called puruṣas. The first, Mahā-Viṣṇu, is the creator of the total material energy [mahat], the second is Garbhodaśāyī, who is situated within each universe, and the third is Kṣīrodaśāyī, who lives in the heart of every living being. He who knows these three becomes liberated from the clutches of māyā.’
Purport: 

This verse appears in the Laghu-bhāgavatāmṛta (Pūrva-khaṇḍa 2.9), where it has been quoted from the Sātvata-tantra.