CC Madhya 21.37
haro harati tad-vaśaḥ
“[Lord Brahmā said:] ‘Following the will of the Supreme Personality of Godhead, I create, Lord Śiva destroys, and He Himself in the form of Kṣīrodakaśāyī Viṣṇu maintains all the affairs of material nature. Thus the supreme controller of the three modes of material nature is Lord Viṣṇu.’
This is a quotation from Śrīmad-Bhāgavatam (2.6.32).