CC Madhya 20.145

vyāmohāya carācarasya jagatas te te purāṇāgamās
tāṁ tām eva hi devatāṁ paramikāṁ jalpantu kalpāvadhi
siddhānte punar eka eva bhagavān viṣṇuḥ samastāgama-
vyāpāreṣu vivecana-vyatikaraṁ nīteṣu niścīyate
Synonyms: 
vyāmohāya — to increase the illusion and ignorance; cara-acarasya — of all living entities, moving and nonmoving; jagataḥ — of the world; te te — those respective; purāṇa — the supplementary Vedic literatures called the Purāṇas; āgamāḥ — and Vedas; tām tām — that respective; eva hi — certainly; devatām — demigod; paramikām — as supreme; jalpantu — let them speak about; kalpa-avadhi — until the end of the millennium; siddhānte — in conclusion; punaḥ — but; ekaḥ — one; eva — only; bhagavān — Supreme Personality of Godhead; viṣṇuḥ — Lord Viṣṇu; samasta — all; āgama — of the Vedas; vyāpāreṣu — in the dealings; vivecana-vyatikaram — to collective consideration; nīteṣu — when forcibly brought; niścīyate — is established.
Translation: 
“ ‘There are many types of Vedic literatures and supplementary Purāṇas. In each of them there are particular demigods who are spoken of as the chief demigods. This is just to create an illusion for moving and nonmoving living entities. Let them perpetually engage in such imaginations. However, when one analytically studies all these Vedic literatures collectively, he comes to the conclusion that Lord Viṣṇu is the one and only Supreme Personality of Godhead.’
Purport: 

This is a verse from the Padma Purāṇa.