CC Madhya 20.318
haro harati tad-vaśaḥ
“[Lord Brahmā said:] ‘I am engaged by the Supreme Personality of Godhead to create. Following His orders, Lord Śiva dissolves everything. The Supreme Personality of Godhead in His 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). Lord Brahmā gave this information to Devarṣi Nārada when he was receiving instructions from Lord Brahmā to understand the Supreme Personality of Godhead, Paramātmā. After describing the universal form of the Lord, Lord Brahmā explained that his position and Lord Śiva’s position are controlled by Lord Viṣṇu.